In the classic Doom games (Ultimate, II, and Final), the IDDQD God Mode code does not actually make the player totally invincible to everything. It only renders the player invincible to attacks that do less than 1,000 points of damage. As a result, a telefrag, which does 10,000 points of damage, will kill a player in God Mode, as can attacks in modified levels that can do that amount of damage as well.

A special floor type (damaging floor of type 11) used in the first game's E1M8 (Phobos Anomaly) will also circumvent and deactivate God Mode.