Guide
How the kit works
Start a fight with Δ Order: Meteoric Incineration when you can. It attacks enemies in an area and applies Fire Weakness to all enemies at the start of each wave for 2 turns. Use Order: Aerial Bombardment to gain Energy: it consumes 40% of Max HP, restores Energy equal to 60% of Max Energy and advances Firefly's next action by 25%. If she lacks enough HP, the Skill leaves her at 1 HP.
Use Fyrefly Type-IV: Complete Combustion once Energy is full. It advances her action by 100%, gives her 60 SPD and unlocks enhanced attacks until the countdown ends. Those attacks gain 50% Weakness Break Efficiency and deal 20% more Break DMG for the current attack. The countdown has a fixed SPD of 70, and the Ultimate cannot be used again during this state.
Use Fyrefly Type-IV: Deathstar Overload to restore 25% of Max HP, add Fire Weakness for 2 turns and hit the target and adjacent enemies. Fyrefly Type-IV: Pyrogenic Decimation restores 20% of Max HP and hits one enemy. Breaking enemies with either enhanced attack delays the countdown by 10%, up to three times per state.
At 150% Break Effect, attacks against Weakness-Broken enemies convert their Toughness Reduction into an instance of 100% Super Break DMG; at 300%, it becomes 150%. Chrysalid Pyronexus provides up to 40% DMG Reduction at low HP, keeps that maximum during Complete Combustion and gives 30% Effect RES in the state. Reaching full Energy also dispels Firefly's debuffs.
Build and why
Use four pieces of Iron Cavalry Against the Scourge. Its 2-piece bonus gives 16% Break Effect. At 150% Break Effect, Break DMG ignores 10% of the target's DEF; at 250%, Super Break DMG ignores an additional 15%. Thief of Shooting Meteor is an alternative with Break Effect on both its 2-piece and 4-piece bonuses.
For the planar set, choose Forge of the Kalpagni Lantern. It gives 6% SPD and 40% Break Effect for 1 turn after hitting an enemy with Fire Weakness, which Firefly can apply herself. Talia: Kingdom of Banditry is another option: it gives 16% Break Effect, plus 20% more at 145 SPD.
Choose ATK Percentage on the body and sphere, SPD on the feet and Break Effect on the rope. Prioritize Break Effect, then SPD, then ATK Percentage in substats. Break Effect supports her Super Break thresholds, while every 10 ATK above 1800 adds 0.8% Break Effect.
Whereabouts Should Dreams Rest is the first weapon choice: it gives 60% Break Effect and applies Routed when the wearer deals Break DMG. Routed makes the target take 24% more Break DMG from the wearer and lowers its SPD by 20%. Thus Burns the Dawn is next, with 12 base SPD and 18% DEF ignore when dealing DMG. Its 60% DMG bonus after Ultimate is removed at the start of the turn. On the Fall of an Aeon is another option that builds ATK when the wearer attacks.
Leveling priority
Follow the game's order: level Fyrefly Type-IV: Complete Combustion first, then Order: Aerial Bombardment, Chrysalid Pyronexus and the Basic ATK. The Ultimate unlocks the enhanced state, the Skill builds Energy for it, and the Talent helps Firefly withstand damage while she spends HP.
For ascension, collect Credit, Raging Heart, Tatters of Thought, Fragments of Impression and Shards of Desires. Skill upgrades use Credit, Tracks of Destiny, Borisin Teeth, Lupitoxin Sawteeth, Moon Rage Fang, Lost Echo of the Shared Wish and the same three Thought, Impression and Desires materials.
The listed maximum costs are 308,000 Credit for ascension and 3,000,000 Credit for all skills. Keep enough of the shared materials for both.
Eidolons worth it
From Shattered Sky, I Free Fall is worth considering for the extra turn. During Complete Combustion, an enhanced attack grants it after defeating an enemy or breaking their Weakness. It can trigger once per turn, with the count resetting at the start of Firefly's turn.
In Reddened Chrysalis, I Once Rest is another useful stopping point: the enhanced Skill ignores 15% DEF and costs no Skill Points. In Finalized Morrow, I Full Bloom is a later option, adding 20% Fire RES PEN during Complete Combustion and 50% Weakness Break Efficiency to enhanced attacks.
You can stay at E0 or stop at E1 or E2. E3 and E5 raise skill levels, while E4 adds Effect RES during Complete Combustion. Consider those intermediate upgrades if you plan to continue toward E6, rather than treating each as a required stopping point.
Teams
Pair Firefly with teammates who support Break or Super Break and someone who can keep the team alive. Lingsha is a Fire sustain option with a Break focus. Fugue is a Fire Break and Super Break teammate, while Ruan Mei is a Break-focused buffer.
Trailblazer (Harmony) is another Break and Super Break buffer to consider in a support slot. The Dahlia is a Fire option with Break, Super Break and sustain tags; Gallagher is another Fire sustain option with a Break focus.
Firefly gives the team Fire Weakness on the enemies hit by her enhanced Skill. Her Technique can apply it to all enemies at the start of each wave, giving Fire teammates targets with that Weakness as well.
Common mistakes
Do not ignore Firefly's HP before using her normal Skill. It can leave her at 1 HP, even though her enhanced attacks restore health. Give the team a sustain option and watch her health between enhanced states.
Do not build only ATK and miss the Break Effect thresholds. Check her stats during Complete Combustion, when she gains 25% Break Effect, and remember that Forge of the Kalpagni Lantern has a 1-turn condition.
Do not assume Complete Combustion lasts indefinitely. Watch its countdown and use the enhanced Skill against suitable targets; breaking enemies with enhanced attacks can delay the timer.
