Dad's Red-ray Disc is a passive item in Glacier's Laboratory, a mod for The Binding of Isaac.

Spawns a Cracked Key every 5 rooms.

When Isaac enters a new room, a number will be displayed at the top of the screen.

The number usually shows the coordinate of current room in white color.

Upon first pickup or entering a new floor, it instead shows the coordinate of Ultra Secret Room in red color.

Isaac can use these two coordinates to find the whereabouts of Ultra Secret Room.

If Ultra Secret Room doesn't exist on current floor, it displays ERR instead.

Dad's Red-ray Disc can be found in the following item pools:

The following tags are applied to this item:

• Download Glacier's Laboratory from the Steam Workshop.