Spawn spot

From Doom Wiki

Spawn spot data
Thing type	87 (decimal), 57 (hex)
Appears in	Doom II/Final Doom
Radius	0
Sprite	(none; FIRE is used as a monster appears)
Class	none

Spawn spots are the targets for a spawn shooter, part of the final boss. They are things defined in the source code, but since they have no associated sprites, they are not directly visible.

The spawn shooter fires skull cubes toward each spawn spot in rotation, in the order they appear in the Things lump. When a cube lands at a spawn spot, anything there is telefragged (even a player in god mode), and a new monster appears in a burst of flames.

There may be up to 32 spawn spots in a level. However, if there are no spawn spots, a spawn shooter will not create any cubes. If there are too many spawn spots, the game will crash immediately after the spawn shooter awakens. This is due to overflowing the array used to store pointers to the spots.