Guide
How the kit works
Before battle, use Skill Showcase to attack. After entering combat, it deals four hits to random enemies, each with a 100% base chance to apply Firekiss. Bladed Hoop also advances Guinaifen's action by 25% when battle begins.
Use Blazing Welcome to hit a target for 120% of Guinaifen's ATK and adjacent enemies for 40%. It has a 100% base chance to Burn those targets. This Burn lasts two turns and deals Fire DoT equal to 218% of her ATK at the start of the affected enemy's turn.
With High Poles, Standing Ovation has an 80% base chance to apply the same Burn as her Skill. Use it when you want to attack one enemy and still have a chance to apply Burn.
While Guinaifen is on the field, PatrAeon Benefits has a 100% base chance to apply Firekiss after Burn deals damage. Each stack makes the enemy receive 7% more damage for three turns, up to three stacks. Watch This Showstopper hits all enemies and makes any Burn already on them deal 92% of its original damage immediately. That Burn damage can also apply Firekiss. Walking on Knives increases Guinaifen's damage against Burned enemies by 20%.
Build and why
For relics, start with four pieces of Prisoner in Deep Confinement. Its ATK bonus helps Guinaifen's damage, and its four-piece effect ignores 6% DEF for each DoT on the target, up to three. Firesmith of Lava-Forging is another option: it boosts Fire damage and Skill damage, then boosts Fire damage for the next attack after her Ultimate.
For the planar set, Revelry by the Sea gives ATK and increases DoT damage when ATK reaches 2400 or 3600. Pan-Cosmic Commercial Enterprise is another option if you want Effect Hit Rate; it also converts part of that stat into ATK.
Use ATK Percentage on the body and rope, SPD on the feet and Fire DMG Boost on the sphere. For substats, follow ATK Percentage, SPD, then Effect Hit Rate. ATK supports her Burn damage, while Effect Hit Rate helps with her base chances to apply effects.
Good Night and Sleep Well is the first weapon to consider: its damage bonus counts debuffs on the target and also applies to DoT. Patience Is All You Need gives damage and SPD, and can inflict Erode, a Lightning DoT. Reforged Remembrance gives Effect Hit Rate and gains stacks from different DoT types, increasing ATK and letting DoT ignore DEF. Eyes of the Prey is another option for Effect Hit Rate and DoT damage.
Leveling priority
Level Blazing Welcome first for its Burn and direct damage, then Watch This Showstopper for its damage and Burn trigger. Follow with PatrAeon Benefits for Firekiss, and leave Standing Ovation until last.
For maximum ascension, you need 246,400 Credit, 50 Searing Steel Blade, 12 Artifex's Module, 13 Artifex's Cogwheel and 12 Artifex's Gyreheart.
To max all skills, you need another 2,400,000 Credit, 5 Tracks of Destiny, 12 Obsidian of Dread, 54 Obsidian of Desolation, 105 Obsidian of Obsession, 12 Regret of Infinite Ochema, 28 Artifex's Module, 42 Artifex's Cogwheel and 42 Artifex's Gyreheart.
Eidolons worth it
Brushing Teeth While Whistling is a good stopping point to consider for a Burn-focused build. It increases the damage multiplier of Burn applied by Guinaifen's Basic ATK or Skill by 40%.
Catching Bullet with Hands is worth considering for team damage: it raises the Firekiss limit by one stack. Slurping Noodles During Handstand is useful earlier because her Skill has a 100% base chance to reduce the attacked target's Effect RES by 10% for two turns.
Blocking Pike with Neck gives Guinaifen 2 Energy each time her own Burn deals damage. Smashing Boulder on Chest and Swallowing Sword to Stomach raise skill levels, so you can treat them as lower priorities if you are stopping early. You cannot skip earlier eidolons on the way to E6.
Teams
Kafka is a good partner for a DoT team. Black Swan or Hysilens can add another DoT character and debuffer. Guinaifen's Firekiss increases the damage enemies receive, so it helps their damage too.
For a complete team, try Guinaifen, Kafka, Black Swan and Gallagher. Gallagher covers the sustain role while the other three bring DoT and debuffs. Natasha is another sustain option.
Asta is a Fire buffer worth considering, while Acheron is another suggested teammate who brings debuffs. No particular allied element is required for Guinaifen's Burn or Firekiss.
Common mistakes
Do not expect the Ultimate to trigger Burn damage on an enemy without Burn. Apply it first when you can, then use the Ultimate while the effect is still present.
A 100% base chance is not the same as a guaranteed application. Do not ignore Effect Hit Rate just because the Skill and Talent list 100% base chances.
Do not build only for direct hits and forget Burn. Her Skill's DoT scales with ATK, and Prisoner in Deep Confinement rewards having DoTs on the target. Also remember that the Basic ATK's Burn comes from High Poles, so unlock that passive before relying on it.