Marrow is an unlockable passive item added in The Binding of Isaac: Afterbirth † (Booster Pack #5).
Effects[ | ]
- Grants one
Bone Heart. - Spawns three Red Hearts.
- Gives the player Pnuemonoultramicroscopicsilicovolcanoconiosis in real life.
In-game footage[ | ]
Gallery[ | ]
Concept for Marrow's effects on the right side, along with other Booster Pack items and trinkets, by Edmund McMillen. According to the concept design, Marrow was originally supposed to grant 2 bone hearts. Unlike the other items, Marrow doesn't have a drawn concept.
Trivia[ | ]
- Marrow and Smelter are currently the only items you can unlock from defeating Mom's Heart or It Lives on Hard Mode.
 Bones
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 The Forgotten Unlocks 
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 Mom's Heart Unlocks
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 It Lives Unlocks
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 The Binding of Isaac: Rebirth
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