Wierd levels with ironman_rooms on

[Ithulta]

Occasionally I'll get a level without any greater vaults. I thought they were always supposed to be superb levels. The first time it was lvl 30 of the SandwormLair. I figured it was because of the guaranteed unique (btw, if I didn't kill her that time, is she just gone?), but it happened again of a few nondescript levels of Moria. What's the reason for this?

[Yottle]

Occasionally I'll get a level without any greater vaults. I thought they were always supposed to be superb levels. The first time it was lvl 30 of the SandwormLair. I figured it was because of the guaranteed unique (btw, if I didn't kill her that time, is she just gone?), but it happened again of a few nondescript levels of Moria. What's the reason for this?

You can get levels with special features: destroyed level, market, and river of lava come to mind. In the Sandworm Lair it would be a destroyed level.

[Ithulta]

Yep, they were destroyed levels. Wow, I just got the "Generation restarted level (too many monsters" message 46 times in row. Had to hold down escape key for a while.