I did some research on how the order of buff synergies, because I couldn't find anything about them online. After doing 2-3 short runs to figure out their connecting paths, I figured I'd make a build that uses all buffs (except Haste, because I hate moving too fast).
The result was pretty intense! I managed to get to OL12 without any issue, and was able to facetank it while being AFK (the gif is OL11 but I got to OL12 later on). The run is literally still on-going in the background as I'm typing this guide, so I'm pretty convinced it works.

The Build

Skill selection
Runes
Have an exact selection of skills, combined with the Prowess rune to ensure you have every buff, or a way to synergize into them, made stronger by the Synergetic rune. Combine with Earth skills because Earthquake is easy damage and Earth Shield provides immense healing.

Core mechanics

Contrary to my other builds, the core of this build isn't a particular skill, but rather scaling buffs to such a degree that your stats essentially don't matter anymore. In order to get all buffs, we need to use synergies to get them. The only alternative is to take skill that grant us the buff directly, but that would require an insane amount of Skill Mastery runes.
If we want to get the synergy passives, we must have 2 sources for the "start" buff. For example, if we want the synergy passive that grants Bulwark when we get Finesse, we must have 2 sources of Finesse already. Once you get a synergy passive, that passive now also counts as a source for that buff, so you can daisy-chain them to get more synergies. Additionally, we can get Prowess from a Rune, which also counts as a source for the synergies.
Combining all buffs (except Haste), we can get damage, crit chance, crit damage, multicast, armor and block. We can get those stats to such a high degree, that choosing any of these as an actual reward becomes borderline useless. If you've already got 2000% increased damage, getting +15% as a rare reward doesn't do much anymore.
What remains is cast frequency, (some) multicast, health and experience. We also need a bit of movespeed to make it a bit more comfortable during the earlier levels, but as we'll completely stop moving around OL8, we don't need too much of it either. Even though we also get multicast from the Finesse buff, it's the one buff that we don't have any synergies towards so it doesn't get quite as high as the others.

Breakdown

This skill uses the Unexpected Arsenal rune to allow all weapon-specific skills to be selected freely.
Skill Selection
For the Bulwark (block) and Finesse (multicast) buffs, we use Whirlwind and Double Slash. Double Slash has the added benefit of also applying the Debilitated debuff on enemies, reducing their damage dealt. Since both skills grant both buffs, we immediately apply for both synergies. However, Finesse synergizes into Bulwark, which we already have 2 sources for. Still, more block is never bad, and it provides an extra chance to trigger Bulwark's synergy, which goes into Aptitude (crit damage). This is our only source for Aptitude, so the extra chance to trigger it isn't unwelcome.
Whirlwind is almost exactly the same as Double Slash, just without the Debilitated debuff.
For Prowess (damage) and Resilience (armor), we primarily use Heavy Strike and the Prowess rune. Like previously mentioned, the rune counts as a source of Prowess and allows us to synergize into Resilience. That synergy passive then becomes the second source, allowing us to synergize Resilience into Form (crit chance).
Heavy Strike also applies Bleed, but we don't actually scale it so it doesn't do much in the bigger picture.
To make the build actually deal damage, we include Earthquake, which is one of the highest damaging abilities in the game, due to the Brittle stacks it applies and the Colossal buff.
Brittle stacks on enemies increases the damage of future hits by a flat value. This means that you're better off using a skill that does a ton of small hits, instead of using slow but heavy-hitting skills. Earthquake itself is a skill that does a ton of small hits, which means it both applies a lot of Brittle, and take great advantage of those stacks. Further more, as you get higher level and start casting Earthquake more often, you'll both apply more Brittle and hit more often, which makes Earthquake particularly powerful.
The Colossal stacks provided by Earthquake also make Earthquake itself hit a much bigger area. With enough multicast and skill-chaining, we can get Earthquake to cover pretty much the entire arena. This is another way in which casting Earthquake faster make Earthquake more powerful in general.
https://preview.redd.it/nacvbt2cyt1d1.png?width=689&format=png&auto=webp&s=c830d93242cc00dd7ab3cf8fb1cb194f8c9bb53f
An easy second choice for an Earth skill is Earth Shield. Not only does it also provide another source of Resilience to allow us to synergize Form from, it also provides massive amount of healing. With the amount of block and armor this build is already stacking, this healing can make us borderline immune to anything but one-shots if we get enough multicast and skillchaining.
https://preview.redd.it/avc1bdtpyt1d1.png?width=395&format=png&auto=webp&s=b7891025b7e59fe2ffeaeaa764a82c5ca2c900ed
For our 6th and final skill, we use Scent of Blood. We've got a pretty big stack of Finesse building and Scent of Blood is just an easy stack of Cast Frequency. It also creates a feedback loop where we get Finesse stacks from attacking, but Scent of Blood makes us attack faster, resulting in more Finesse stacks, make Scent of Blood stronger, and so on. This makes scaling Scent of Blood slow at first, but once it picks up, it is easily maxxed out.
Do be aware that the Cast Frequency provided by Scent of Blood doesn't apply to Scent of Blood itself. You'll need to scale some skill-specific cast frequency for Scent of Blood, and keep an eye out for any Duration passives as well to get 100% uptime.
https://preview.redd.it/akimp052zt1d1.png?width=397&format=png&auto=webp&s=51109cb4fadbdd8099315a8788795c64b451f546
Mechanics
Skill-chains
As always, skillchaining is the main way to scale the build, as it allows you to bypass the long cooldowns. The most important one is Swing-to-Earth, since we really need a ton of Earthquake and Earth Shield casts to get end-game damage and healing. Swing-to-Slam is also fine for getting more Prowess and Resilience stacks.
Synergies
Synergies are really what makes this build work. It's the best way of scaling our buffs into the ridiculous amounts. There's not much to be said about them, since they're just passive rewards, but they are on par with some legendary rewards for this build.
Skill Choice
The Earth kills I chose are largely because Earthquake is mega-OP and Earth Shield honestly is as well. You could probably swap them out for Holy skills without losing too much, since they also provide some healing, but I don't think you'll be able to deal as much damage. If you don't mind losing the healing, I doubt there's a skill you couldn't make work with this setup.

Rune choice

https://preview.redd.it/7n2ha8be0u1d1.png?width=368&format=png&auto=webp&s=d4e4c319b8d3f794cd7a214c5b6d6cc30769c593
Versatility Runes:
It's the usual combo of Endless Refill and Reroll Mastery to get easy skills selection, and we need Unexpected Arsenal to get acces to Heavy Strike. I wanted Heavy Strike since it's fast, but it's not a requirement for the build specifically.
You could swap out Unexpected Arsenal for anything you want, but then you need to change Heavy Strike for any other skill that at least grants Prowess. I'd recommend Armor Shatter. It's a bit slower, but it does provide the Shattered debuff, which might be nice.
Tenacity Runes:
The most important one by far is the Divine Legacy rune, which is (in my opinion) easily the best rune in the game. By cleverly saving and using your locks only at every 25th level, you can get 3 legendary passives every 25 levels, which is just crazy. This is probably true for almost every build, so you'll see this section in a lot of my builds.
Synergetic is super important for really getting the most out of the buffs you get from your skills, as is the case for any build that focuses heavily on buff or damaging debuffs.
You need the Battle Proficiency rune for triggering the Prowess into Resilience synergy, but that synergy isn't mandatory for the build to work since Earth Shield already grants Resilience. It's probably the best choice, but you can swap it out as needed.
Critical Mastery is super effective for our build since we can reach around 1000% crit chance at our highest point through Aptitude stacks. That's an easy extra 250% extra crit damage, which is pretty significant.

Stat priorities

These are the priorities for "basic" stats. Skill chain, type-synergies ( like "more damage per ice skill for non-ice skills", and legendary rewards are almost always better.
Prioritize in order:
Buff Synergies
Any buff synergy is good, even those that provide armor or block. Buff Synergies are so good, I personally consider them on-par with several Legendary passives don't do as much for our build (like Physical Damage for example).
Health
It's a bit weird to have Health listed this high, but in reality, we really don't need much else. Our buff provide such insane base stats, that we really don't need to worry about our damage output.
Rest
You might want to get some Cast Frequency or other stats at first to get the build going, but it's really not necesary to overinvest. It might not make your start the quickest, but this is a marathon-build, not a sprinter. Likewise, you'll probably want some movespeed to make dodging easier, but you won't be need to do much dodging in the end-game, so don't go overboard. Increased Experience is honestly pretty good for this build, since most of your power will come from the Legendary skill-chain and multicast passives and boosting Scent of Blood to get your cooldowns lower.

That's the build!

It's not very suprising that stacking a ton of buffs would result in a killing machine, but I didn't quite expect to be so unkillable. This was definitely one of the more fun builds to do, since I had to figure out which buffs synergize to what and which skills to take to get the daisy-chain started effectively.
In the GIF that I linked at the start of this post, I actually did the build semi-wrong, since I didn't take the Prowess rune (even though I intended to at the start). I only later noticed that it was missing, and only then found out that Earth Shield also provided Resilience, so that was pretty lucky for me. Fortunately, you guys have this build so you don't need to make the same mistake I did :)
If you haven't seen it, please have a look at my previous build, the Conflagrate Barbarian.

You may also check this guide at https://docs.google.com/document/d/1wt1e7uSzrrNgprYYTbobxdyk4zVnK3p761WbjnbhinU/edit?usp=sharing

Kit Explanation

Firefly is a 5-star Fire Destruction character. Her kit focuses around two phases:
The basic state, with a skill that costs 40% of her max HP to gain 60% of her max Energy; and the Complete Combustion state she can enter for a limited time by using Ultimate.
In Complete Combustion state, Firefly gains an enhanced Basic Attack and Skill, a good amount of SPD, Weakness Break Efficiency which lets her break enemies faster, and Super Break DMG against broken enemies.
The enhanced attacks in Complete Combustion state (enhanced state for short here on out) also heal herself. The Enhanced Skill implants a Fire weakness on all targets. In both forms, Firefly also takes reduced damage the lower her HP is, and gains bonus Break Effect based on her ATK.
In short, she cycles between a form that sacrifices HP to get energy, and a stronger form that gets huge benefits from Break.
Firefly has a kit with powerful dual stat scaling, no innate supportive capabilities and high SP consumption, which means her best role is that of a Hypercarry supported by multiple amplifiers.

Sample Setups

These are merely samples! You can choose your teams freely, there’s good freedom for the sustain in particular. For replacements, check the sections further down the guide. For different supports, use their regular builds.
Standard Team: Firefly, Harmony Trailblazer, Ruan Mei, Gallagher
This is the default Break team, highly synergistic and what most people will be running. It requires a single extra limited character in Ruan Mei, and has very high payoff. Gallagher, Break Firefly’s best sustain from a damage standpoint, is a free event reward in Firefly’s patch.
Budget Team: Firefly, Harmony Trailblazer, Asta, Gallagher
A team featuring 3 free characters and Firefly, for anyone who doesn’t have Ruan Mei. Has very high performance for the cost.
Firefly
LC: Whereabouts Should Dreams Rest > On the Fall of an Aeon > Indelible Promise
Relic Sets: 4-Pc [Iron Cavalry Against Scourge], or [2-Pc Break Effect set bonus + 2-Pc Break Effect set bonus] + 2-Pc [Forge of the Kalpagni Lantern], or [Talia]
Main Stats: ATK% Body / SPD Boots / ATK% Sphere / Break Effect Rope
Substats: Enough SPD to get to 210 in enhanced state, then as much Break Effect as possible (ATK% also good, not as good as BE)
Harmony Trailblazer
LC: Past Self in Mirror > Memories of the Past > Meshing Cogs
Relic Sets: 4-Pc [Watchmaker], or [2-Pc Break Effect set bonus + 2-Pc Break Effect or SPD set bonus] + 2-Pc [Talia], or [Forge of the Kalpagni Lantern], or [Fleet]
Main Stats: HP% or DEF% Body / SPD Boots / HP% or DEF% Sphere / Break Effect Rope
If you only have one Past Self in Mirror or Memories of the Past, HTB has priority on using the better one, as it uses both better than Ruan Mei. HTB has priority on using Watchmaker as well.
Substats: Enough SPD to be faster than Firefly and/or meet Talia’s requirement, then all-in on Break Effect (middle priority to improve)
Ruan Mei
LC: Past Self in Mirror > Memories of the Past > Meshing Cogs
Relic Sets: 4-Pc [Watchmaker], or [2-Pc Break Effect set bonus + 2-Pc Break Effect or SPD set bonus] + 2-Pc [Vonwacq], or [Penacony], or [Fleet]
Main Stats: HP% or DEF% Body / SPD Boots / HP% or DEF% Sphere / Energy Regen Rope
Substats: Break Effect (minimum 100%, can stop at 160%) + SPD (middle priority to improve)
Asta
LC: Meshing Cogs
Relic Sets: [2-Pc Break Effect set bonus + 2-Pc Break Effect or SPD set bonus] + 2-Pc [Penacony], or [Fleet]
Main Stats: HP% or DEF% Body / SPD Boots / HP% or DEF% Sphere / Energy Regen Rope
Substats: Enough SPD to be faster than Firefly, then all-in on Break Effect, more SPD is good too (low priority to improve)
Gallagher
LC: Multiplication / What is Real? (Multiplication is priority if it feels safe enough)
Relic Sets: [2-Pc Break Effect set bonus + 2-Pc Break Effect or SPD set bonus] + 2-Pc [Talia], or [Forge of the Kalpagni Lantern], or [Fleet]
Main Stats: Outgoing Healing Body / SPD Boots / HP% or DEF% Sphere / Energy Regen Rope
Substats: As much SPD as possible, Break Effect is good as well (low priority to improve)
Note: The Planar set bonuses are the least important part of the builds for anyone but Firefly. If you get the main stats on other sets, or even incomplete sets, it’ll only result in a minor decrease in team performance.

Stat Building

Speed
210 SPD while transformed is not detailed in a trace, but is the requirement for Firefly to get a 4th action within her Ultimate without external sources of action advance, and also 3 actions on a wave change while the countdown is currently on the action bar. Because of that, it’s extremely important to attain this breakpoint.
Reaching it will generally require SPD boots, together with another source of speed, like the Forge set bonus, substats or smaller buffs such as Ruan Mei’s talent.
A stable 165 SPD while untransformed, equaling 225 SPD while transformed, is the breakpoint for getting 3 Enhanced Actions in the first cycle without any external Action Advances. This speed will require a decent amount of substats, but is worth considering if and only if 0-cycling is one of your goals
Break Effect/Attack
Firefly’s main scaling stat is Break Effect, as most of her damage is Break DMG. She also converts ATK into BE, which makes ATK% very close to BE for her scaling per percentage. Since BE sources often give out more than ATK% sources, BE is still the higher priority.
There is a breakpoint of 360% BE for her personal Super Break DMG, and that should be attained by all means, which should not be difficult with proper support and heavy BE investment. Attaining more BE by all means is how Firefly does her damage.
Critical
No.
Her multipliers and several other benefits towards building Crit have been completely destroyed with Beta v3. Crit stats are completely wasted on Firefly.

Light Cones

Whereabouts Should Dreams Rest, her signature LC, is the best option as with every DPS in the game. Break Effect is uncommon in Destruction LCs, and this gives a big chunk of it together with a debuff that helps Firefly deal Super Break DMG.
Its importance for her seems to be about average when compared to other DPSes’ signature options for themselves - she is not as signature-reliant as Blade or Acheron. Aeon, mentioned below, is a great F2P replacement.
On the Fall of an Aeon, the Herta Store LC, gives Firefly a huge chunk of ATK%, which gets converted into more BE. It also has very high base ATK to increase the value of other sources of ATK%. This should be your default F2P choice.
Indelible Promise is her best 4* option, giving a good amount of Break Effect, the stat she wants the most. It does need a high Superimposition to be great, which is something inaccessible to most players.
Flames Afar, mentioned here due to the frequent talk about it pre-beta, is not a good option for Firefly despite Sam being in it. Firefly needs BE or ATK% for her damage scaling, and Flames Afar offers neither of them, so its effect is useless on her.
Other Light Cones are inferior and not recommended.

Relics and Planars

Iron Cavalry Against Scourge, a set being introduced together with Firefly’s release in 2.3, is her undisputed best option. Break/Super Break DMG is the majority of Firefly’s damage profile, and the significant DEF ignore is one of the biggest sources of damage increase you can have.
2-Pc/2-Pc Set combos are a great option for Firefly. With 3 sets that give BE to mix and match between, you can pick the combinations with the best BE substats you can find. Iron Cavalry’s improvement is sizable, but the performance of 2-Pc/2-Pc sets is still high enough for re-farming to not be necessary.
Genius of Brilliant Stars, aka Quantum set, is also a solid option. It also features DEF ignore stacking that works on Break DMG, but will provide less of it in most situations and also has a worse 2-Pc effect. Just as above, if you’ve saved up Quantum pieces with high Break Effect, they’ll serve you well.
Longevous Disciple, mentioned here due to the frequent talk about it pre-beta, has several issues with uptime and not giving Firefly one of her two scaling stats, so its effect is useless on her.
Other set options are not recommended, as they’ll be outdone by 2-Pc/2-Pc builds.
Planar Sets:
Forge of the Kalpagni Lantern and Talia: Kingdom of Banditry both give massives amount of Break Effect to contribute to your main damage and are almost identical in benefit. Both of their conditions are automatically met in enhanced state.
All other options are worse. Typically, the gap between Planar sets for characters is quite small, but the Break sets offer a lot of that stat, and since it’s unlikely to have good BE pieces saved up in other sets, it’s recommended to farm either Forge or Talia.

Team Building - Amplifiers

Harmony Trailblazer - Firefly and Harmony Trailblazer’s kits seem to have been practically made for each other. HTB’s biggest fault of only buffing Break Effect is fixed by Firefly’s kit converting it directly into damage scaling, while Firefly’s high innate BE and incredible break value on Enhanced Skill will help her deal extremely high Super Break DMG. These two should be together in teams at basically all times.
Differently from Boothill, who doesn’t use HTB in his most optimal teams, Firefly has more upfront break to access Super Break DMG quicker, especially with the help of Gallagher or Bronya, and can’t trigger default Break DMG by herself. In general, Break characters are highly recommended to stick together, both to amplify each other and to get Super Break DMG, so the other two currently in the game, Ruan Mei and Gallagher, go very well here.
Ruan Mei - A fantastic fit, almost every part of Ruan Mei’s kit greatly benefits Firefly. Weakness Break Efficiency helps her break enemies faster and improves Super Break DMG, RES PEN is a modifier that also works on Break damage, and the passive SPD and BE help Firefly get to her thresholds. An easy choice to put into any team.
Ruan Mei’s E1 will be a good improvement to these teams, with its DEF ignore stacking with Iron Cavalry’s set bonus for exponential growth.
Asta - Asta is a good budget option for Break teams when lacking 5* Harmony units. Her ATK buff is directly converted into more BE for Firefly, and the high break value on her skill means she can deal significant Super Break DMG and help Firefly break enemies faster.
Asta’s speed buff can give Firefly’s enhanced state a fourth turn with no speed investment, but it can only be ready for the first one in specific conditions - an E6 Asta with Meshing Cogs, an ERR rope and using technique instead of Firefly’s. Because of that, it’s recommended to still run Speed boots on Firefly.
Asta is recommended to build towards Break Effect in her substats as she doesn’t have high stat requirements elsewhere.
Hanya - Hanya’s benefits are very similar to Asta’s, but Asta is a free character with upsides to Hanya. Use Hanya as a budget option if you just don’t like Asta.
Bronya - Bronya works incredibly well with Firefly. More actions in Enhanced State have very high value, and Bronya gives more than any other support. With E0 Firefly’s SP consumption, though, those teams need to finish fights incredibly quickly before they run dry of SP. When Firefly is E1, Bronya becomes a better option.
The required speed tuning for optimization is pending with v3 changes, but is likely to be very demanding on Bronya’s side.
Silver Wolf/Pela - Both of these characters help stack DEF reduction, which affects Super Break DMG. The damage increase from this is solid, and they can be considered budget options.
Robin - Almost none of Robin’s benefits work with Firefly, as her ATK buff does not contribute to Firefly’s ATK > BE conversion. With that in mind, Robin ends up being close in performance to Asta as a teammate. Even if she’s E1, just use her on your other team.
Tingyun - Tingyun’s main appeal, the energy battery, is of low benefit to Firefly. Since Firefly’s Enhanced Skill generates no energy, Tingyun needs Huohuo to cut a turn of downtime. Her ATK buff is beaten out by Asta, and most other benefits are wasted.
Sparkle - Sparkle’s DMG% and crit buffing is entirely wasted on Firefly. Her Action Advance is extremely difficult to make use of with Firefly’s changing speed and will not give many enhanced actions.
Yukong - Yukong’s skill’s value is practically tossed out the window with Firefly’s self-action advance and speed buff. With her ATK% buff being unreliable and Yukong providing nothing else towards Firefly’s breakpoints, she’s not a good option at all.

Team Building - Sustains

Firefly is not very picky with sustains. Even still, there are some preferences. Her high SP consumption favors sustains that can generate high amounts of SP.
Gallagher - Gallagher is a perfect fit for Firefly. Generating insane amounts of SP due to his ultimate’s action advance and Multiplication, coupled with helping break Fire weak enemies which Firefly creates and increasing their Break DMG received, Gallagher can be considered the optimal sustain from a damage standpoint despite his 4* status.
E1 is an important breakpoint for Gallagher, letting him contribute massive amounts of Break before Firefly’s first action to let her break enemies quicker. Gallagher does this by using Skill to get to full energy on his first turn > Ultimate > Enhanced Basic.
Other Fast Abundances - This includes Natasha, Lynx, Bailu and Luocha. Having high speed on these helps make up for Firefly’s SP consumption to give your support units more freedom, and since the DPS is typically the weak link of the team survivability-wise, Firefly’s innate tankiness helps mitigate the weaker healing provided by Natasha, Lynx and Bailu. Multiplication is recommended, but if it feels too unsafe, feel free to use a more healing-oriented LC.
Aventurine - Firefly does not have any reservations against being played with a shielder. Her self-action advance happens infrequently enough that it shouldn’t lead to Aventurine’s shields falling off, and with Firefly being tankier than most DPS, Aventurine’s need to use skill decreases even more, making him a very safe sustain option that also provides good SP.
Huohuo - Huohuo’s SP consumption is a poor fit for Firefly, the ATK buff from her ultimate lasts too little to be worth much, and the energy battery is useless for Firefly herself unless you waste another slot on Tingyun. Huohuo is still a strong character against any CC-heavy fights and smooths out most supports’ rotations, though.
Fu Xuan - Fu Xuan’s low SP generation is an issue when being ran with Firefly, but if that’s accounted for with your other support choices, Fu Xuan functions moderately well - she’ll still be as safe as she is with anyone, but her Crit buff will not benefit Firefly at all.

# Eidolons

As with most other characters, E3 and E5 are minor numerical upgrades that don’t change the kit’s workings. Their pictures are linked for your appreciation, though.
E1 - In Reddened Chrysalis, I Once Rest): DEF ignore is the rare modifier to apply to Break DMG, making it a solid damage increase. The Enhanced Skill not consuming SP moves Firefly’s average SP consumption from around -1.4 SP/t to -0.55 SP/t, which is quite significant in giving more team options as well.
E2 - From Shattered Sky, I Free Fall: The newest busted, whale-bait eidolon. Adding functionally two turns to ultimate state is a hilariously powerful effect, and it’s very easy to make use of it - your Blast attacks will often break main targets and kill adds quickly.
This eidolon is undoubtedly broken, but same as with Acheron’s and Imbibitor Lunae’s, it is not required for Firefly to be a strong character by any stretch of the imagination. Do not feel forced to go for it if you can’t afford it.
E4 - Upon Lighted Firefly, I Soon Gaze: A token effect that is typically covered by your sustain unit. Never worth stopping at.
E6 - In Finalized Morrow, I Full Bloom: RES PEN and Weakness Break Efficiency will both greatly help with your Super Break DMG.
A strong eidolon by itself, but considering its cost is functionally quadrupled due to the minor benefits of E3-E5, the benefit-cost ratio is very low, and if your goal is to increase Firefly’s performance the most you can, early upgrades to supports will be of bigger benefit to her than aiming for E6.
https://preview.redd.it/eankui4swt1d1.png?width=685&format=png&auto=webp&s=3e28efdf1fa9f2543f8d1994949f017297613c24
Q: Don’t Ruan Mei and Harmony Trailblazer have anti-synergy with Firefly, since they delay their Break recovery, so you can’t Break them again?
A: With a well-built team, not at all. Even without these delays, enemies will die before being broken twice almost unconditionally. In that case, it’s better to extend the benefits you get from attacking broken enemies, so these delays are a strict upside.
Q: E1, Signature LC, literally anything else OR Ruan Mei?
A: Ruan Mei, and it’s not close. The benefit she provides to Firefly’s damage is unmatched, and she can be considered an essential teammate to maximize Firefly’s damage.
Q: Signature LC or E1?
A: Both are decently close in performance. I’d give the edge to Signature for most players, freeing up your Aeon for use with other Destruction characters.
Q: Does Crit or DMG% affect Break damage?
A: No. The only Relic stat that increases Break damage is Break Effect. The only buffs/debuffs that do are Break Effect increases, DEF reduction/ignore, RES PEN, and Damage Taken increases.