While in the battle, you can tap and hold the Buff icon and read what it does.
The Feather effect varies depending on the hero:
- Chicko ( Passive Ability and Ability 2)
Each stack of Feather deals additional 10% Damage.
- Roxy (Passive Ability and Abilities 1,2, 3)
Each Stack of Feather reduces incoming damage by 5%..
If an ally has a Feather stack, Roxy can also apply a random buff, or for allied Kaggie or Boreas — 2 buffs.