The zombie walk override token is a rare item from the Walk Like a Zombie promotion. It could be won from Treasure Hunter during the promotion. Claiming the token unlocks the Zombie Walk override permanently without having to complete the fleshy parchment five times. Claiming the token destroys it.
This item was not always awarded when completing the fleshy parchment five times; the override was unlocked directly if a token wasn't used to unlock it before. If a token was used before, another was rewarded by completing the parchment five times.