ToME WikiMt Doom is a SpecialLevel on DungeonLevel 99 in a branch of the dungeon Mordor. This special level is persistent, meaning that it can be used to transfer object between characters(!). It is the only special level that stays in place even after you leave it once, making it very special indeed.
The persistent feature should make your careful of what you do with the level; thaumaturgy has been known to produce glass wall that seal off this level forever!
Chatter
MayLith: This page is confusing the special level and the dungeon. I'm going to split the two out.
TheFalcon: You might also wish to investigate the persistentness of walls and object transfer when you do. (See discussion on the Spoiler forum).
BobVin: Genocide doesn't work on this level.
TheMimic: Yeah, it'd be good to know if there is any way to bypass poorly placed glass walls here. Maybe a temporary adjustment of a file would be considered legitimate? Or perhaps you can delete the file that governs the persistence of this stage?
NerdanelVampire: Switch Position should get you through glass walls and works even on no-teleport levels unless my memory is going entirely. Have you found the Ring of Flare yet?