Creates a new room adjacent to a viable wall, indicated by the outline of a door. These rooms have a chance to be various special rooms.
Quote
"Explore the other side"
Effects
Allows Isaac to create new rooms by using the key next to a wall where there would be no conditions that could prevent a (secret) room from spawning there. This indicated by walls that have red door outlines on them.
These rooms are most commonly normal rooms, but have a chance to be various special rooms instead, even including red Devil Rooms or red Angel Rooms.