Tonsil is a trinket added in Afterbirth †.
- When hit, there is a small chance a removed tonsil familiar starts following Isaac, blocking enemy shots.
- The effect can happen twice, after which the trinket will be destroyed.
- The familiar does not deal damage to enemies.
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- When the familiar is generated, Isaac will gain the familiar permanently as a passive item. This allows Isaac to drop the trinket while keeping the familiar.
- The passive Tonsil item does not exist in any item pool; thus, this is the only way to find it and make it appear in the Collection Page aside from starting with it as Eden.
- If Eden starts with the passive tonsil item and picks up the trinket, the trinket will spawn only one familiar before being consumed.
- On average, each familiar spawns after approximately 16 hits. 
- Tonsils are soft tissue located near the back of the throat which can be removed without much noticeable difference.