It's the Key#327

Achievement · Afterbirth †

Description

Unlocked a new item.

Unlocked by

Defeat The Lamb without taking Hearts, Coins, or Bombs through the entire run. Letting certain familiars (e.g. Bum Friend, Dark Bum, Bumbo or Lil Portal) or bosses (e.g. Bumbino) pick up the consumables fails this condition as well.https://www.youtube.com/watch?v=5WmLk8m0lxY