Although only its head is visible, the endgame text indicates that the entity has a gigantic body as well.
In Doom 2, it appears as a massive, goat-like biomechanical head on a wall, with a surgically exposed brain that allows it to spawn endless scores of demons.
Red (Doom Eternal), white (Doom 2) The Icon of Sin is the final boss and is encountered in Doom 2 and Doom Eternal.
