From Sonic Retro
The Warrior Feather or Sage Feather (in the Japanese version) is an upgrade available to Amy in Sonic Adventure. It takes the form of a red-and-white hair accessory, and enables the hedgehog to use the Spin Hammer Attack, a circular move like a stationary version of Tails' Tail Swipe. Sonic Adventure is the only game where the Spin Hammer Attack is seen, and so this upgrade has not appeared anywhere since.
- Purpose: Allows Amy to use the Spin Hammer Attack.
- Location: Egg Carrier interior, in the Hedgehog Hammer minigame outside the ship's brig. Unlike all the other characters' upgrades, the Feather is not found lying on the floor with a green effect; it is automatically awarded on winning the minigame.
- Requirements: None; just beat Robotnik's high score at Hedgehog Hammer.
- Required For: Nothing--it's purely a novelty item to make Amy's life easier when surrounded by badniks. You do, however, have to win Hedgehog Hammer to escape from the brig, so it isn't possible to avoid getting the upgrade.