Key



Keys are used to open designated locked doors. There are two types of key; futuristic keycards, and "skull keys", which resemble glowing monochrome skulls. If the player encounters a locked door and attempts to open it without the correct key, the door will not open and the player will get a message saying so. Once a key is obtained, any locked door of corresponding color on the map can be opened. Keys are lost upon map exit.

Doom does not differentiate between keycards and skull keys. Boom however introduced door types that require the key to be of the right type and not just the right color. Such doors are supported in most source ports.

Appearance statistics
The IWADs contain the following numbers of keys of each type:

Blue keycard Red keycard Yellow keycard

Blue skull key Red skull key Yellow skull key