Fujiwara no Mokou as a phoenix. While Mokou isn't an actual phoenix, she is frequently associated with them due to being a pyrokinetic immortal and producing a phoenix-shaped aura with some of her spellcards.
Depictions of Mokou as a phoenix are usually chibi-styled, and either include Ex-Keine as a sukusuku hakutaku or group Mokou with chibi-bird form versions of Touhou's bird-youkai characters.