As with most other aspects of megadungeon design, it's a never-ending process. Dwimmermount is constantly changing, as I restock and alter it in response to player actions. In running my play by post version, I've added a few new wrinkles as well, the first that the players have so far encountered being the monsters known as eldritch bones.
Eldritch bones are the reanimated skeletons of slain soldiers. Unlike most other types of skeletons, eldritch bones are not undead. Rather, they are magical constructs brought back to a semblance of life through the use of minute quantities of azoth, which not only gives them the ability to move and attack but also strengthens their bones. Consequently, eldritch bones have a metallic appearance, thanks to the silvery-black azoth that suffuses them.
The process of creating them was originally an invention of the Eld, but was perfected by the Thulians during their late, Termaxian phase. Like truly undead skeletons, eldritch bones suffer only one-half damage from sharp/edged weapons, while blunt weapons do full damage. They are immune sleep, charm, and hold spells and are unaffected by holy water.
The material in the quote box below is hereby designated Open Game Content via the Open Game License.
Number Appearing: 3d6
% in Lair: Nil
Armor Class: 5
Hit Dice: 1+1
Attacks: 1 weapon (1d6+1)
Hoard Class: Nil
Create Eldritch Bones
Level: Magic-User, 6th Level
Range: 10 feet
Provided the caster possesses an ampule of undiluted azoth, this spell enables the creation of eldritch bones from the complete skeletons of humanoid beings. 1d6 eldritch bones are created per level of the caster above 11th. The eldritch bones remain animated until destroyed.