Fel is one of the options for the Stage 6 Boss. Fel's fight starts with a 70 health/0 attack Alabaster Guardian on each floor. Fel can have one of three additional effects:
- Eternal Crest: Alabaster Guardians have Spell Shield 5, and Fel empowers units on a floor with armor.
- Wrath Crest: Alabaster Guardians have Multistrike, and Fel empowers units on a floor with Rage.
- Scouring Crest: Fel and allies will dump Scourge cards into your hand.
If you see you have Scouring Crest Fel at the beginning of the run, I strongly suggest taking Ember after the first boss to help counteract it.
Outside of this, Fel travels from floor to floor before starting her relentless phase. By this point you should have the damage to easily cut through her, with the issue being getting through the Alabaster Guardians in time to keep the Pyre from being overwhelmed.