Crawl sometimes generates unusually hard out-of-depth (OOD) monsters to keep you on your toes. The possibility of out of depth monsters increases the longer you spend on a level (although the overall spawn rate progressively slows after 3,000 turns on that level, stopping altogether at 15,000 turns; see scumming for more details).
- OODs do not apply to any portal vaults, any 1-level branches, Zot, Pan, Abyss and Hells.
- OODs do not apply for the first 700 turns on D:1, and are applied slightly less often for 584 turns on D:2.
- All other levels have a straight 14% chance of moderate OOD fuzz for each monster at level generation, and the chances of moderate OODs go up to 100% after a ramp-up period. After 7800 turns, all the monsters are moderately OOD.
- Under normal circumstances, the max possible difference is 5 levels.
- There are two mechanisms for generating "super out-of-depth" monsters; one can generate monsters up to (current level * 2) + 4. This is the one used by vaults: the glyph used in vault definitions is an '8'; the other is current level + an average of two random numbers between 0 and 26. Super OOD monsters are quite rare, unless you scum on a floor for several thousand turns. They can happen after you reach 1400-117*depth turns (e.g. on D:13, they can happen at level generation) and the initial chance is 0.02%. After 3000 turns have passed, the chance increases until you reach 12,000 turns, at which point all monsters generated (if any) are created using the second super OOD method only.
- Vaults will often contain overly powerful monsters: the vault designer can put in a random OOD monster via the above mentioned "8" glyph, or can specifically hard-code a difficult monster in a vault that can appear early on.