When used in a Challenge Room, opening the door and leaving while the fight is on will continue the music even after you leave until the clip ends.

This does not work on floors where the Devil/Angel Room cannot open by defeating the boss, such as Basement/Cellar 1, Cathedral, The Chest, Sheol, or Depths/Necropolis 2.

If used in a Boss Room before the boss has been defeated, Dad's Key will open the Devil Room/Angel Room.

This could also symbolize how Isaac's father left him and his mother, in much the same way it allows Isaac to leave rooms.

This may indicate that Isaac's father was kind of at least protecting Isaac from things, being able to help him escape in-game.

It was first added to the Wrath of the Lamb DLC for the original game.

When activated in the moment an item drops in a room, it will cause an additional item drop. The item does not open rooms which require a normal key to open, such as Shops, Treasure Rooms, or Libraries. Void is Apollyon 's starting item, it's Eternal, meaning it can't be stolen, destroyed, or sacrificed. Put an active monster that isn't being attacked or a shop item into discard. Discard your hand (Loot Cards), then draw cards equal to the number of cards discarded. This includes the locked door in The Chest or The Dark Room to fight Mega Satan. You can help The Binding of Isaac: Four Souls Wiki by expanding it. On top of the much-anticipated mod support, Afterbirth+ also features 69 new items scattered across new levels, a collection of new enemies and bosses, a new character, and many new ways to kill poor little Isaac.

Upon activation, all closed doors in the current room Isaac is in will be opened this includes Challenge Rooms, rooms in The Chest, and even rooms where there are bosses and enemies (except for the fight with Mom.). With the Binding of Isaac Rebirths second expansion, series creator Edmund McMillen is handing the reigns over to the community.

Binding of isaac the void