Old folks sayings

(continuation of part 2)
III. e) The Mobius FF x FFVII collaboration
Alright, back to our suspension world-hopping! Let’s visit the realm of Mobius FF, —more specifically, the collaboration between Mobius FF and FFVII—, where I found the most substantial evidence for my theory.
In case you’re unfamiliar with the Mobius FF (MFF) world and games, let’s begin with a bit of a summary of the parts relevant to us. The story takes place in a world called Palamecia, to which people from other worlds are inexplicably summoned. The vast majority of those who are brought there don’t remember anything from their worlds of origin or their lives before Palamecia except their names: these amnesiac people are called Blanks. The main character is Wol, accompanied by a guiding fairy of Palamecia named Echo. Echo knows a lot about the mechanisms of Palamecia, as she’s tied to the realm. The leader of this world is Vox, a being who manifests only as a voice. The first thing all Blanks remember before they wake in Palamecia is Vox telling them the rules of the realm. Incidentally, the crystals of the MFF world are teleportation crystals.
III. e) i. Devs’ Statements
Let’s review some of the MFF x FFVII Remake collaboration devs’ statements before diving into its story.
For both the MFF x FFVII Remake collaboration and the Remake project, Kitase took on the role of producer while Nojima supervised the screenplay and wrote the scenario. The project leader was none other than the Remake trilogy’s Hamaguchi, who told a SE interviewer the following:

“We would love for you to play the [MFF x FFVII] collaboration event as you look forward to [Remake’s] release” (“Celebration of the Overseas Release of the Steam Version and FINAL FANTASY VII REMAKE Collaboration Event”, Square Enix).

He later hints at the collaboration’s storyline:

“This collaboration is focused on Cloud, so the other characters will not make an appearance. Players will join Cloud, who has gone astray in Palamecia, on his adventures and see how the story unfolds based on his decisions. Content-wise, FINAL FANTASY VII fans will surely become fraught with emotion as events unfold in-game (laughs).”

Kitase concurs on the emotional aspect of the collaboration in the same interview:

“When it comes to the story, I seek two things– ‘mystery’ and ‘[…] emotional impact’.”

Clearly, fans of FFVII are supposed to react emotionally to the events of the collaboration. With these statements in mind to give us perspective, we can get into the plot points relevant to our analysis. MFF x FFVII Remake comes in two parts, the relevant plot points of which I will describe and analyze one at a time.
III. e) ii. Eclipse Contact
1) Fact-Finding
Part one of the MFF x FFVII Remake collaboration event is called Eclipse Contact. It came out in 2017 on Aerith’s birthday, February 7th, and its release campaign ran until March. In Eclipse Contact, Palamecia welcomes someone new: Cloud Strife appears in the realm with very little recollection of his core world of FFVII.
Cloud isn’t a Blank, since he recalls the mako reactors in Midgar upon his arrival in Palamecia, and also remembers that he was hired by Avalanche to blow them up:

“Echo: How did you end up in Palamecia?

Cloud: I… That day... I remember now. A job. I had taken a job. I was hired muscle protecting clients. They wanted to stop the reactor... We used a train to get past security... Was it at night? Something happened... Next thing I knew, I was floating through darkness. Then [I woke up here]”.

This piece of dialogue reveals that Eclipse Contact Cloud’s memories end at the very moment when Avalanche arrives at reactor 1 in OG (disk 1, chapter 1): the very beginning of the game. Consequently, Cloud does not remember anything that happened from the beginning of the OG timeline onwards.
Wol and Echo are intrigued by Cloud’s strange case: non-Blanks rarely arrive in Palamecia. The following text appears on the screen shortly after they meet:

“Perhaps he is not truly who he thinks he is.
Perhaps everything is illusory, a dream.
Only one thing is certain, that he must press on, one step at a time, toward the light that shines from the promised land.”

Just like he did in FFT’s Ivalice, Cloud feels the need to find the Promised Land in MFF x FFVII, despite the fact that he lacks memories of the OG timeline. Though Cloud doesn’t remember anything beyond the train ride to reactor 1, he does remember the Promised Land (at least somewhat). This is odd, given that in OG, Cloud didn’t learn about the Promised Land until several chapters into the game.
Wol and Echo agree to help Cloud figure out why he’s here, since there’s clearly something strange going on with his presence in Palamecia. In fact, Cloud brought Midgar’s mako reactors with him somehow, transplanting them onto the landscape of Palamecia. The group decides to bomb these reactors, following Cloud’s instincts in the hopes that it will jog his memory.
Now for my favorite part. After blowing up another reactor, the group is surprised by the appearance of a crystal. A piano rendition of Aerith’s theme begins. When Wol tries to touch the crystal, something akin to a force field rejects him. When Cloud approaches it, however, the crystal responds to his hand by flashing with light. As it begins to glow, Wol concludes that the crystal is linked to Cloud and Cloud alone. Let’s examine the resulting dialogue:

“Echo: This is the light in your memories. The light of home.

Cloud: Home? But I don’t—

Echo: If you don't remember… then your home is lost to you.

Cloud: Then my memories are gone.

Wol: Do you want to reclaim your past?

Cloud: Not interested... I am what I am now. Not what I was.

Wol: Then tell me… This light. If you can’t remember it, what does it mean to you?

Cloud: It's a warm light... I feel at peace. If this place —home— is as warm and peaceful as this light, then I want to go there.

Echo: You can't go there... Not back to the past.

Cloud: I see.

Echo: But even if you can't go back to the past, you can go forward. If you wish for it strongly enough, the crystal will show you the way. The way to a new world. The way to your Promised Land. […]

Cloud: So... Should [I] take [my] chances and make a wish to this crystal?

Wol: Go ahead. It’s your crystal.

Echo: I should warn you that once you start on this journey, there's no coming back.

Cloud: The past is the past. I want to go to a place where everything is new. I’m ready.“

What follows is a moment I call the wishing scene (13:43-14:34). Cloud closes his eyes and wishes on the crystal. It flashes, and suddenly, rainbow-colored ripples of light appear around it. Aerith’s theme is replaced by a slightly modified version of “Midgar, City of Mako”, the track that plays during the opening cutscene of Remake. You can recreate the modification by listening to “Midgar, City of Mako” from 2:00 to 2:23, then skipping to 3:00 and listening until 3:18. You may recognize the musical motif that kicks off the wishing scene as the Lifestream motif, which has become symbolic of the mysteries of the Remake trilogy, as it often plays during scenes where unexplainable plot deviations from OG occur— more specifically, deviations involving multiverse shenanigans. For instance, it plays during MOTF 4. It also plays in Rebirth after Cloud blocks masamune as Aerith is shown dying anyway.
Cloud disappears with his crystal, after which Echo speaks to Wol about Cloud’s journey:

“Echo: Each person gets the Promised Land they justly deserve, not the one they really need. If you’re a bad person, you go to a bad place. If you expect nothing, you get nothing. Even the journey there makes you look deep within yourself to find out who you really are. Cloud should be facing his own past as we speak. It’s cruel, but necessary. That battle was a long time coming”.

Apparently, at least in the context of this collaboration event, the Promised Land can be a reward or a punishment, depending on which you deserve. Echo explains that Cloud will have to face himself and his past on his way to his Promised Land. This means that the Cloud that appears in Eclipse Contact must next embark on a journey that will confront him with his past, test his mettle, and ultimately lead him to the Promised Land he justly deserves.
III. e) ii. 2) Fact Analysis
There’s a lot of vital information to dig into here, mostly provided by Echo. She claims that the crystal’s light is linked to Cloud’s memories of home; Cloud has to have known this home in the past, as it could not otherwise exist in his memories. MFF Cloud must be a post-OG Cloud. Unfortunately, Echo indicates that whatever Cloud’s home is, he’s lost both it and his memories of it. Despite this, Cloud describes his home as warm and peaceful, concluding that he wishes to find it. Though Cloud can’t return to the past, Echo tells him that if he wishes it strongly enough, the crystal can guide him toward a new world, where his home and his Promised Land exist in the future. The fact that Aerith’s theme is playing all throughout these descriptions of Cloud’s lost home, his Promised Land and the past that he can’t return to makes it extremely obvious that these concepts all point to Aerith. Aerith is Cloud’s lost home. Wherever Aerith is, that’s his Promised Land. The time spent with Aerith before her loss is the past he tragically can’t return to. You might have clocked the similarities between Eclipse Contact’s mention of Cloud’s lost home and DFF’s mention of Cloud’s lost dream: in both these titles, Cloud’s home and dream are equivalent to his Promised Land. It’s confirmed yet again that Aerith is the one Cloud hopes to return to, just like every soul returns to the Lifestream. At this juncture of my research, I was curious as to why the last thing Cloud remembers before waking in Palamecia is the run-up to the Reactor 1 bombing mission in OG (disk 1, chapter 1). This mystery will have to persist for a while longer.
The alarm bells in your head might’ve been triggered by the mention of the wishing scene’s rainbow ripple effects— and rightfully so. This visual cue has sparked passionate debate in the fandom since its appearances in Rebirth, as seen in these pictures:
Zack Choosing To Get A Cure For Cloud, Rebirth Chapter 14; Creating a New World/Timeline
Aerith Pushing Cloud Out of that World/Timeline, Remake Chapter 14
Cloud Blocking Masamune, Rebirth Chapter 14; Creating New World/Timeline
You might have read or heard that this rainbow effect signifies that a character has entered another timeline, created a portal to another timeline, created a new timeline or is being shown different timelines. Indeed, whenever the OG timeline is deviated from in a significant way, this effect appears. The pictures above present multiple examples of these shifting realities.
One might propose that the rainbow ripples in Eclipse Contact and Rebirth are unrelated because of the long period between their respective release dates. This long in-between period indeed makes it likelier that the effect was used without forethought in Eclipse Contact, forgotten over the years, and incidentally reused in Rebirth as a plot-important visual cue with no connection to Eclipse Contact. I’m inclined to disagree since the crystal is specifically described as a vessel that can take Cloud “to a new world” by Echo, which is a bit on the nose. Regardless, it’s plausible that there’s no connection. That is, it would be, if the rainbow effect didn’t show up in Remake too.
When the Whispers are finally defeated in chapter 18 of Remake, a burst of the rainbow ripple effects indicate the emergence of multiple worlds, newly freed from the restrictive clutches of fate (1:16:36-1:16:47). Shortly thereafter, Sephiroth takes Cloud to the Edge of Creation and invites him to join forces with him. Cloud refuses, and Sephiroth says the following:

“Seven seconds till the end. Time enough for you. Perhaps. But what will you do with it? Let's see.”

The question “What will you do with it?” implies that the answer is unknown, meaning Cloud is no longer bound to the OG timeline by fate: many alternate futures lay ahead. Sephiroth is telling Cloud and the audience that now, the mystery of the Remake trilogy has become “Which future will Cloud bring into existence? Which among the infinite possible timelines will his choices result in?” After pondering this aloud, Sephiroth leaves Cloud alone to consider the rainbow effects in the sky (1:19:23-1:19:36). Because they generally represent alternate or changing timelines, it’s safe to assume that the rainbow ripples here represent the myriad of possible worlds that Cloud’s actions in those seven seconds could generate. After all, Sephiroth was just talking about them, and chapter 18’s description in Remake reads as follows:

“In a world beyond, Sephiroth shows Cloud a vision of the planet seven seconds before its demise. Having strayed from the course destiny set for them, they strike out on a path towards an unknown future."

This explains why the player is shown Cloud staring at those colors in the apocalyptic sky at world’s end, directly after hearing Sephiroth’s cryptic words: those are all the alternate “unknown future” timelines ahead of him, now unravelled from fate. Amongst those rainbow ripples lies the answer to the question “What will you do with [the seven seconds]?”
Given that Remake was released in 2020 and Eclipse Contact came out in 2017, the major story elements of the Remake trilogy —including the eventuality of alternate timelines— had to have been planned out at the time of Eclipse Contact’s release: while the MFF x FFVII Remake collaboration was being made, Remake was also in production. Also recall that the collaboration event and the Remake trilogy share a codirector in Hamaguchi, a writer in Nojima and a producer in Kitase. Based on all this, it’s more than likely that the rainbow ripples in the Remake trilogy and inEclipse Contact represent the very same thing: alternate worlds and timelines. All this to say that when the rainbow effect appears around the crystal in the Eclipse Contact, it means the crystal is acting as a vessel to another world, just like Echo said.
But that’s not all Echo said: she also mentioned that this other world would take Cloud to his home, to his Promised Land. We’ve already established what that means for Cloud, what it’s meant since two whole decades at the time of Eclipse Contact’s release: this crystal will take Cloud to Aerith. So, where exactly did the crystal take Cloud? In what world can he meet Aerith again?
The music that plays during the wishing scene gives us a huge hint. As I noted before, the track playing in the background is a slightly modified version of Remake’s “Midgar, City of Mako”, which plays in the introduction cutscene of Remake. This is a musical cue that the ending of Cloud’s journey in Eclipse Contact and the very beginning of the Remake trilogy are closely related. Add the fact that the devs wanted players to experience this collaboration event before playing Remake, and it becomes undeniable: the crystal that appeared to Cloud in Palamecia —which offers to lead him to his home and Promised Land, meaning to Aerith—, took him to the world of the Remaketrilogy.
Eclipse Contact is huge. The whole crux of my theory lives and dies right here. However, we still have part two of the MFF x FFVII Remake collaboration event to analyze as well as its promotions to look into before I can drop the thesis on you, so bear with me in order to receive the most thorough analysis of all this possible! I want to give you every drop of proof I can!
III. e) ii. MFF x FFVII Remake Fatal Calling
1) Fact-Finding
Fatal Calling came out February 1 of 2018, and its release campaign ended in March. The game opens with a cutscene: Cloud is floating, seemingly unconscious, through a sparkling, green current of light. The current flows into a circle of bright, white light, surrounded by rainbow ripple effects as Cloud is driven toward and into it. An orb floats along with him. The Advent Children theme “The Promised Land” plays, a choir of mournful, aching, mutedly desperate souls engaged in a lamenting prayer. Sephiroth’s voice echoes:

“Sephiroth: It’s time. You may turn your back on the past, lock your memories away. Hide reality beneath a layer of illusion. But destiny will not die so easily. Yes. At memory’s end you may plead for it all to go away. But the past is a curse, binding your soul. It’s time. Wake to your fate. Rise to your destiny.

Cloud: (In a half-conscious grunt) Reunion…

Sephiroth: The light will lead you. Wake to your fate. Rise!”

Sephiroth’s mentions of Cloud hiding under an illusion and repressing his memories are no doubt allusions to Cloud’s past, which was complicated and darkened by Hojo’s experiments. It makes sense, then, that Cloud responds with “Reunion”. Fatal Calling indeed focuses on Cloud’s relationship to his past, his identity and Sephiroth. Everything involving Nibelheim —where everything started—, Sephiroth’s manipulation, and Hojo’s experiments are on the table. Also noteworthy if not out of place is Sephiroth’s evocation of fate.
Cloud enters a battle with Sephiroth with the help of Wol and Echo, who are surprised to see him back in Palamecia. Cloud tells them about the orb seen floating along with him in the opening cutscene: though he calls it a materia, he doesn’t know how or when he acquired it. Based on his behavior, it appears that Cloud remembers just as little about the events of OG as he did by the end of Eclipse Contact. Wol informs Cloud that whoever he heard speaking to him on his way here was probably Vox pretending to be Sephiroth.
As the group advances, Cloud recalls Midgar and decides they should go there next. At one of Midgar’s mako reactors, the group encounters Sephiroth, who speaks to himself:

“It's still not enough. This... this is but a pale imitation of the power I desire.”

Once Sephiroth has disappeared, Cloud explains what he remembers: Sephiroth was the greatest SOLDIER of all and a hero to Cloud, though Cloud can’t remember what exactly ended this admiration. As players of FFVII OG, we know the event in question is the Nibelheim incident, wherein Sephiroth slaughtered the town’s residents, including Cloud’s mother, after learning of his past. The former war hero also severely injured Tifa, whom Cloud presumed dead when he found her in the old mako reactor with a vicious slash on her chest. Cloud is agitated by the gaps in his memory, so the group resolves to follow Sephiroth for answers. When they find him again, Sephiroth causes Cloud to experience a piercing headache with the mere mention of the Reunion. They fight, but Sephiroth is too powerful— he skewers Cloud with the masamune and taunts his unconscious body:

“Sephiroth: A puppet. I won’t kill you. Not yet. Not until you know true despair.
Wol: If you want despair, we got plenty to go around. Palamecia’s full of it.
Sephiroth: Yes, this planet knows suffering. But it is not the world that was promised to me. I must go home. Tell Cloud, if he wants to see me again, he should face his memories. I will await him there, in the land of memory, where it all began. In Nibelheim.”

Sephiroth darkens Cloud’s materia, turning it black. Later, Wol explains to Cloud that Sephiroth stole the light from his materia, taking Cloud’s strength along with it.
Once Cloud has woken up, the group travels to Nibelheim to uncover the truth about Cloud’s memories. Cloud slowly gathers pieces of his past, shown to the player as titled, diary-like text written from various perspectives. Cloud learns the truth about SOLDIER, Jenova cells, Sephiroth, and what happened in Nibelheim. Let’s examine a few of these diary entries:

“A Warrior’s Tale: There's a girl in Nibelheim I think about. Warm. Cheerful. More grown-up than a child. Haven't talked to her much, but she seems nice. She's going to be leading the SOLDIERs to the mountain reactor. Maybe if I get into the survey team I'll get a chance to talk to her? Nah. She's out of my league.”

Young Cloud’s crush on Tifa is on full display! This must be a memory from his time as an infantryman accompanying Zack and Sephiroth to Nibelheim.

“Tale of the Nameless: I drift along in the mako, asleep. Who am I? Who am I? Who am I? Who am I? Give me a number. I… I… I am… The Reunion. The Reunion must happen.”

This entry could be taken from any one of the Nibelheim survivors’ perspectives, as they were all bathed in mako and turned into Sephiroth clones. I would venture to say this is Cloud’s perspective though, given the reference to this iconic line from OG:

“Cloud: Professor... please give me a number. Please, Professor...
Hojo: Shut up, miserable failure.” (disk 2, chapter 2).

The trio encounters Sephiroth near the old Mt. Nibel mako reactor. Because Sephiroth stole the light from his materia earlier, Cloud goes into the confrontation already drained of his strength. However, when Cloud lifts the materia in his hand, it lights up and creates rainbow ripples in the air around him, similar to those seen in Eclipse Contact and Rebirth. Cloud is healed of his injuries: he closes his eyes for a moment, wearing a peaceful expression. Sephiroth is displeased, but recovers quickly:

“Sephiroth: The guiding light… it healed you.

Wol: […] here, near the mako reactor, the materia regained its light. And your strength returned […]. [Sephiroth]’s here so he can steal the power you've stored inside that materia.

Sephiroth, with a short laugh: I have all the power I need. Cloud. What strength you’ve regained is yours. Use it to fight me. It’s time. Let’s decide this, in this land lost to despair. The prize is home. The Promised Land. There to answer the call of destiny.”

With this second evocation of fate, Sephiroth disappears.
Cloud, Wol and Echo find Sephiroth at the Northern Crater. He mocks Cloud for believing the orb in his possession is materia. Sephiroth waves a hand and his signature black and purple fog surrounds Cloud, immobilizing him. Sephiroth claims that the power Cloud regained at the Mt. Nibel reactor was Sephiroth’s all along. Now that it courses through Cloud’s veins, Sephiroth controls him. He calls Cloud his puppet and finishes with the following before the two vanish, leaving Wol and Echo alone:

“Now, let us return. Back to the Promised Land. The time of the Reunion has come.”

After Cloud finally breaks free and defeats Sephiroth with the help of Wol and Echo, the villain makes a final threat:

“Very good, Cloud. You’ve destroyed an illusion. But the time will come to abandon your illusions and face reality. Then, you will know true pain.”

Sephiroth disappears for the last time, his body surrounded by his signature dark fog and the rainbow ripples. A piano rendition of Tifa’s theme begins. Cloud’s orb rises into the air and becomes a crystal, with the same shape and glow as the one we see in Eclipse Contact. The following dialogue is illuminating:

“Cloud: I will fight. The light will lead me where I need to go.

Wol: You sure? Wasn’t that [crystal] Sephiroth’s?

Cloud: I heard Sephiroth's voice, at the end. Inside me. Whatever he put in me, it’s still in there. Someday I’ll settle that score. If I can't avoid destiny, I might as well face it head-on.

Wol: Yeah. That was quite a speech, Cloud. Surprised you made it through without laughing.

Cloud: Yeah, forget I said it. I will too.

Echo: Forgetting won’t make it go away. Even if the words fade from memory, your dream will never disappear. Not until it becomes real.“

The crystal shines as though in response.

“Echo: See? See, that's how the light of hope works. Hope can turn your dreams into reality.

Cloud: Yeah. I guess so. I might forget this world, but I won’t forget hope. And my reality, that’s for me to live.”

Tifa’s theme ends. Cloud approaches the crystal, and disappears in a beam of blinding light. Once Cloud has vanished with the crystal, Aerith’s theme begins playing. A few pale feathers with a slight orange tint (the color of MFF) float down onto the floor where he stood seconds before. The image fades to black. The credits roll, and Aerith’s theme continues all the way through.
Once both the final name in the credits and Aerith’s theme fade, we’re surprised by a sudden, troubling image: Sephiroth appears in a frightening flash, standing amidst the flames of Nibelheim. When his image fades to black, the collaboration title *“Final Fantasy VII x Mobius Final Fantasy”*appears on the screen. The FFVII title is surrounded by the 1997 meteor logo. Then, a flash of light: the titles reappear, except this time, they read “Final Fantasy VII REMAKE x Mobius Final Fantasy”. The new Remake Meteor logo replaces the 1997 version. As soon as these changes to the FFVIItitle and meteor logo occur, Aerith’s theme returns. It plays on until the game ends a few seconds later, the screen fading to black.
III. e) ii. 2) Fact Analysis
The introduction cutscene shows that MFF Cloud travelled from Eclipse Contact to Fatal Calling via Lifestream. It’s unclear how much time has passed in between, but the atemporal nature of the Lifestream makes the question irrelevant. My theory that MFF Cloud has died is corroborated by the way he’s depicted in the opening cutscene: his eyes are closed and his body is limp as the Lifestream carries him.
Eclipse Contact ended with Echo’s claim that Cloud will face his true self and confront his past while he journeys to his Promised Land. This description resembles what Cloud experienced in the OG Lifestream sequence (disk 2, chapter 8). Indeed, Fatal Calling revolves around the same topics the Lifestream sequence addresses: the truth about the Nibelheim incident, Hojo’s experiments, young Cloud’s crush on Tifa, etc. The opening cutscene shows Cloud being transported to his Promised Land and facing his past on the way there, just like Echo said he would.
Let’s now take a long detour to examine the song that plays during the opening cutscene of Fatal Calling: “The Promised Land” theme from Advent Children. The title and general subject of this song are obviously relevant to the cutscene, but there must be more to its inclusion than that. Perhaps the lyrics can help us understand its appearance in the opening cutscene of Fatal Calling. Here are the unofficial English lyrics (translated from the original Japanese lyrics by an anonymous fan and verified by me via DeepL):

“Why do we cling together?
Why do we give punishment to lesser hearts?
The planet did not forgive us
Did not forgive us
The planet did not forgive us
Did not forgive us
The pulse of veins flows through the earth
A faint, faint pulse
Of a heart drawn to death
A gentle life returns to the planet
Is it necessary to sacrifice souls?
Why do we cling together?
Why do we beg for forgiveness
In the Promised Land?” (“‘The Promised Land’ (theme)” by Final Fantasy Wiki).

The song appears to be a regretful lament of human behavior, expressed by the repetition of “Why do we […]?” questions. The behaviors listed are all typically human ones: the terms “[clinging] together” and “[giving] punishment to [the] lesser” express the uniquely human nature of tribalism and the consequences of the fear and hatred it can generate, and “[begging] for forgiveness in the Promised Land” is likely a reference to the human hypocrisy of only feeling sorry for one’s crimes when judgement day arrives. This last line describes a scenario where someone remains passive or ignorant in the face of something important, only to realize its essentiality once it’s too late. The repeated“The planet did not forgive us” lines reflect the fear of being condemned forever because of one’s mistakes, as though the planet is a deity one has sinned against. The lyric describing a pulse in the earth is obviously about the planet being alive— a reference to the Lifestream. But the pulse is faint and weak and the planet is dying, perishing because of mankind’s greed. This is an indictment of mako energy. The line “A gentle life returns to the planet” refers to an innocent’s soul returning to the Lifestream after death, while the next lyric “Is it necessary to sacrifice souls?” protests the “sacrifice” of the planet’s soul energy for mako production. In all this darkness, this song’s mention of “forgiveness in the Promised Land” leaves a modicum of hope for a better place, however meek, even though mankind might not deserve it. The song “The Promised Land” is both a lament of mankind’s ways and a plea for mercy, with religious and/or spiritual undertones. The song’s themes seem to be: the Promised Land itself, regret and shame, the sins and foolishness of mankind, the death of innocents, grief, Cetra spirituality, and a meek, quiet hope despite it all. The most interesting aspect of the song is its antithetical portrayal of death as a thing of both despair and hope, condemnation and salvation, cruelty and mercy, suffering and relief. Maybe we can glean more information about this theme’s significance in the world of FFVII if we examine the contexts in which it appears.
Importantly, the song plays in Marlene’s introductory narration of Advent Children, meaning its themes are related or similar to the film’s. I highly recommend listening and watching it again, even if you remember this iconic segment. Marlene references Aerith’s sacrifice as the image of Cloud lowering her into the water is shown. Note that Marlene says “Sadness was the price to see it end” (2:36) after we are shown Aerith’s death and her subsequent unleashing of the Lifestream (1:49-2:24): Aerith’s innocent life was sacrificed for the planet’s survival. The lyrics “A gentle life returns to the planet” and “Is it necessary to sacrifice souls?” suit Aerith’s situation quite well.
The theme also plays in Advent Children as Kadaj dies in Cloud’s arms (1:45:00-1:47:55), hearing Aerith’s gentle voice and reaching up to take her invisible hand. Here is what Aerith says to him in his dying moments as “The Promised Land” plays:

“Aerith’s voice: Kadaj?

Kadaj: Huh?

The dark sky has gone with Sephiroth. Healing rain starts falling from bright clouds. The rain no longer hurts Kadaj.

Aerith’s voice: You don’t have to hang on any longer.

Kadaj: Mother! Is that…?

Aerith’s voice: Everyone’s waiting, if you’re ready.

Kadaj nods his head slightly in acceptance. He holds out his hand, and slowly evaporates into the Lifestream. Cloud watches […]” (Advent Children).

Kadaj is brought into the Lifestream by Aerith as she provides rain from the Lifestream. All those with geostigma are healed by the rain, and Tifa feels Aerith’s presence as the party celebrates:

“Tifa, looking out at the falling rain […]: Somehow, I knew you were there. Thank you” (Advent Children).

Cloud stands in the rain with a smile —his first in the whole film—, closes his eyes and basks in Aerith’s healing with his face upturned. He is finally at peace:

“Cloud’s expression is one of peace as the [Lifestream] rain patters against him” (Final Fantasy VII Advent Children English script, “[83] Atop the Shinra Building”).

One thing is clear: the track “The Promised Land” accompanies Aerith. It only makes sense, since we’ve seen overwhelming evidence that she is Cloud’s Promised Land, and since she occupies the Lifestream —which some consider the Promised Land as it is where souls go after death— during the events of Advent Children. Note that when the piece plays, Cloud is shown either mourning Aerith and releasing her into the river at the Cetra capital, or basking in her presence, smiling with relief at the peaceful feeling that she’s somewhere near: these two opposing scenes reflect the song’s antithetical portrayal of death.
Additionally, the song’s themes of regret, shame concerning one’s sins and a small hope perfectly describe Cloud’s character arc and feelings in Advent Children. Cloud regrets his inability to save Aerith, which he considers a sin. Further, he only realized how important she is to him once it was too late to tell her. And of course, he harbors a fragile yet important hope that he’ll be reunited with her in the Promised Land:

“‘Can sins ever be forgiven?’ — Cloud asks this to Vincent, who mutters a brief answer. For both of them, ‘I couldn't protect my loved one’ is the sense of guilt that they carry, so their words resonate with weight” (FFVII 10th Anniversary Ultimania Revised Edition, “Chapter 2: Character in FFVIIWorld”, “Vincent Valentine”, “In Advent Children”, page 72).

"’It is my sin that I couldn't protect my loved one’ — under this assumption, Cloud closes off his heart. What will the reunion with Aerith bring him? ‘I... think I want to be forgiven. Yeah, I just want to be forgiven’” (FFVII 10th Anniversary Ultimania Revised Edition, “Chapter 2: Character in FFVIIWorld”, “Cloud Strife”, “In Advent Children”, page 40).
“Cloud, after seeing Aerith’s hand reach for him through the Lifestream: … I think I'm beginning to understand.

Tifa: What?

Cloud: An answer from the Planet… the Promised Land... I think I can meet her... there” (disk 3, chapter 3).

Just as the song and Marlene express in the introduction of the film, Aerith was innocent, and her sacrifice generated great grief. Cloud finally experiences peace when he feels her presence in the healing rain, and he smiles: he’s glad to be with her again, even if it’s only for a brief moment of tangential respite.
The scene depicts Aerith guiding Kadaj into the Lifestream as the song plays, tying her to the concept and theme song of the Promised Land once more. This connection is later solidified by Tifa’s thanks to the late flower girl. All of this evidence shows us that this musical theme is intimately linked to Aerith, as it never plays in her absence. After all, the song speaks of sins, the death of innocents, forgiveness, grief, a small sense of hope, regret and the afterlife: all themes relevant to Cloud’s feelings surrounding Aerith’s death in and outside of Advent Children.
The Remake OST also includes a version of this piece called “The Promised Land - Cycle of Life”. This iteration of the theme begins playing in the wake of the first bombing mission, right after Sephiroth taunts Cloud with his mother’s dying words in Sector 8 (chapter 2). Sephiroth appears to Cloud surrounded by flames, evoking the Nibelheim massacre, and the theme begins playing in the background once he disappears, continuing (13:17-15:30) as Cloud walks through the sector, encountering fires and destruction all around him. This version of the Promised Land theme is meant to emphasize the deaths of the innocent Nibelheim townsfolk and the innocents in Sector 8. This dreadful atmosphere is amplified by the cries of despair that ring all around as Cloud passes by NPC Sector 8 residents. Perhaps the themes of tribalism and mankind’s sin are relevant to this scene as well, since Shinra and Avalanche are two distinct and warring groups whose quarrels, regardless of their necessity, result in the deaths of innocents. The theme of guilt also emerges, reflecting the Avalanche members’ feelings upon seeing the unintended collateral damage of the explosion. “The Promised Land - Cycle of Life” plays until Cloud encounters Aerith on Loveless. So it seems in this scenario, the heavy weight of death and despair is lifted when Cloud meets the lively, cheery Aerith. Once more, Aerith is central to the musical theme of the Promised Land, as well as to the concept itself.
I also noticed that a version of the song plays as Cloud and the party ready to enter the Forgotten Capital to save Aerith in Rebirth’s chapter 14: it truly adds the weight of her upcoming death to the scene.
Back to Fatal Calling, the scene where Cloud regains his strength is quite mysterious. Wol says Cloud’s orb regained its “guiding light” light because of its proximity to the mako reactor. In the moment his strength is replenished, Cloud is shown tilting his head back and closing his eyes: this is reminiscent of the scene in Advent Children when he stands under Aerith’s healing Lifestream rain, feeling at peace. The rainbow ripples shining from the orb indicate that something is crossing the boundaries of worlds. Since the mako reactor pumps up the Lifestream, being near a reactor also means being physically near the Lifestream. This means Aerith’s spirit is within proximity. In my opinion, Aerith was able to heal Cloud from the Lifestream, just like in Advent Children. However, Aerith is not in Palamecia with him: her healing had to travel there through the Lifestream, transcending the boundaries of worlds, hence the rainbow ripples.
Let’s now address the appearance of Tifa’s character theme in Fatal Calling. Since Fatal Calling is all about discovering Cloud’s past in Nibelheim and then in Hojo’s lab, it makes lots of sense for Tifa’s theme to play as the crystal appears. In OG’s Lifestream sequence (disk 2 chapter 8), she’s the one there helping Cloud sort through his past instead of Wol and Echo. Cloud even picks up a piece of his childhood crush on Tifa in Fatal Calling as a shard of his memory. After all, this crush was the catalyst for him joining SOLDIER, and everything that transpired in consequence:

“Cloud: That was the first time I heard about Sephiroth. If I got strong like Sephiroth, then everyone might... If I could just get stronger... Then even Tifa would have to notice me” (FFVII OG, disk 2, chapter 8).

Additionally, it’s fitting that her theme should begin right after Sephiroth speaks of “[abandoning] your illusions and [facing] reality”, considering that Cloud’s false persona was concocted by Jenova using Tifa’s mistaken impressions of Cloud:

“While being tended to by a station worker in the Sector 7 Slum train station, [Cloud] was reunited with Tifa, and using the abilities of Jenova’s cells, formed a new personality” (FFVII 10th Anniversary Ultimania Revised Edition, “Chapter 2: Character in FFVII World, “Cloud Strife”, “Cloud Behavior Record, Compilation of FFVII”, page 40).
“(Image caption:) A new personality takes shape the moment he sees Tifa” (FFVII Story Playback, “Story Check: Tifa’s Flashback”).

“Tifa (to Cloud): Deep down, you're a pretty nice guy. Didn't see it when we were kids, but...” (Remake, chapter 14).