The monster spawner fires its cubes toward each spawn spot in rotation, in the order they appear in the THINGS lump. When a cube reaches a spawn spot, a burst of yellow flames is rendered, and a hellish monster (excluding the two major bosses) appears in the location. If the spawner and its spawn spots are placed in MAP30 any cube landing at a spawn spot currently occupied by a player or monster will telefrag it. If the boss-related things are placed in another level, however, the new monster and the thing currently occupying its location will simply become stuck together.