Rune Bag is an unlockable passive item added in the Binding of Isaac: Afterbirth expansion.
- Spawns a familiar that drops a random rune alternating every 5 or 6 rooms ( 7 or 8 rooms).
- If there are no runes unlocked, it will drop cards instead.
- Rune Bag will also drop Soul Stones if any have been unlocked.
- If not every rune is unlocked, it will drop a Rune Shard in place of the corresponding rune.
- BFFS!: The drop rate is improved to every 4-5 rooms.
- The drop rate is improved to every 6 rooms.
This item is the rune counterpart to Bomb Bag, Mystery Sack, Sack of Pennies, and Sack of Sacks.
PC H46A 1PJE (Treasure room adjacent to spawn)
Switch 9XX3 HWL2 (First Golden Treasure Room)