Guide
How the kit works
Start Yanfei's field time with Signed Edict if an enemy is in range. A hit deals AoE Pyro DMG and gives her the maximum number of Scarlet Seals. Spend them with the Charged Attack from Seal of Approval (NA), then use Normal Attacks to build seals again. Normally she can hold up to three; hitting with another Normal Attack refreshes the duration of the seals she already has.
Use Done Deal when available and follow it with a Charged Attack rather than immediately using the Skill: both abilities give a full set of seals. The Burst also grants Brilliance, which increases Charged Attack damage and gives her seals at fixed intervals. Brilliance ends when Yanfei leaves the field or falls, so give her time to use it.
Proviso grants 5% Pyro DMG Bonus for six seconds per seal consumed by a Charged Attack. A new Charged Attack replaces the previous effect. Blazing Eye adds AoE Pyro DMG equal to 80% of ATK when a Charged Attack scores a CRIT Hit; that extra hit counts as Charged Attack damage.
Build and why
The first set to look at is four-piece Crimson Witch of Flames. Its two-piece gives 15% Pyro DMG Bonus, while the four-piece increases several Pyro reaction damage values. Using the Skill also increases the two-piece bonus by 50% of its starting value for 10 seconds, up to three stacks.
Four-piece Wanderer's Troupe is another strong option: it gives 80 Elemental Mastery and increases Charged Attack damage by 35% for a Catalyst user. Shimenawa's Reminiscence boosts those attacks by 50% for 10 seconds after the Skill, but consumes 15 Energy if Yanfei has enough. That cost matters when you want her Burst. Martial Artist is another option for Normal and Charged Attacks.
Use ATK Percentage or Elemental Mastery on the sands, Pyro DMG Bonus on the goblet, and CRIT Rate or CRIT DMG on the circlet. For substats, look for CRIT Rate and CRIT DMG first, then ATK Percentage, Elemental Mastery and Energy Recharge. CRIT Rate also helps trigger Blazing Eye.
Lost Prayer to the Sacred Winds is the first weapon choice: it gains an 8% Elemental DMG Bonus every four seconds in battle, up to four stacks. Skyward Atlas gives 12% Elemental DMG Bonus and can produce an extra attack from Normal Attack hits. Flowing Purity gives Elemental DMG Bonus after the Skill, with a further bonus when its Bond of Life is cleared. The Widsith is another option, though its 10-second buff is random.
Leveling priority
A good leveling order is Seal of Approval (NA) first, Done Deal second and Signed Edict third. Yanfei repeatedly uses Charged Attacks during her field time, so improving them is a useful starting point. The Burst deals damage and supports those attacks; the Skill still matters for its damage and full set of seals.
For ascension, collect Mora, Noctilucous Jade and Juvenile Jade, along with Agnidus Agate Sliver, Agnidus Agate Fragment, Agnidus Agate Chunk and Agnidus Agate Gemstone. You also need Treasure Hoarder Insignia, Silver Raven Insignia and Golden Raven Insignia.
Talent upgrades use those three Insignia materials and Mora as well. They also need Teachings of Gold, Guide to Gold, Philosophies of Gold, Bloodjade Branch and Crown of Insight.
Constellations worth it
The Law Knows No Kindness is a useful early upgrade. Each existing Scarlet Seal reduces the Stamina cost of a Charged Attack by a further 10% and increases resistance to interruption during its release. It makes spending seals easier while Yanfei is on the field.
Supreme Amnesty adds a shield when Yanfei uses her Burst. It absorbs damage up to 45% of her Max HP for 15 seconds and absorbs Pyro damage 250% more effectively. It is a useful defensive option, though its capacity depends on Max HP.
Extra Clause is worth considering for a damage build because it raises the seal limit by one. Right of Final Interpretation gives Charged Attacks 20% more CRIT Rate only against enemies below 50% HP. Samadhi Fire-Forged and Abiding Affidavit raise Skill and Burst levels respectively. You can leave those upgrades aside when planning around her basic Charged Attack pattern.
Common mistakes
Do not use Signed Edict and Done Deal back to back without considering the seals: both grant the maximum on a hit or cast respectively. A Charged Attack between them lets you spend one full set first. Avoid switching away with seals still held, since they disappear when Yanfei leaves the field.
Do not leave the field immediately after the Burst if you want its Brilliance effect. Watch Stamina and incoming attacks during the short Charged Attack cast, especially before C1 or without a shield.
Do not focus only on ATK Percentage and ignore CRIT Rate: Blazing Eye needs a Charged Attack CRIT Hit. Also account for the Energy cost of Shimenawa's Reminiscence if it leaves you unable to use the Burst when you want it.
