While monsters do not normally spawn once you enter a floor, some effects or branches may generate new monsters as you stay in it. Specifically, there is a "monster generation rate" (MGR), and every 5 turns, there is a (5 in MGR) chance of a monster spawning somewhere on the level; a higher value means a slower spawn rate. This monster will normally fit the branch it was spawned in. The MGR's value varies:
- Pandemonium: MGR starts at 50; after 3k turns, it gradually rises (slows down) until it reaches 300, at 15k turns.
- Abyss: set to 5, meaning that there will always be a monster spawn every 5 turns.
- During the Orb run: set to 18. Monsters spawn near you, with a special monster set:
Otherwise, monster spawn is disabled.
- Prior to 0.23, the Orb run's spawn set was more likely to spawn weak monsters, but at a faster rate.
- Prior to 0.21, most of the permanent branches in the Dungeon naturally spawned monsters over time. Spawns would turn out of depth, mostly after 3k turns have passed. Monster spawns stopped after 15k turns.
- Orb run spawns were changed in 0.13: the most notable additions were Orb Guardians and eyeball monsters.
- Prior to 0.6, there was no special function to create out of depth monsters when staying in one area.