Undead Earth Elemental (Undead, Elemental)--Montporte Dungeon Campaign Critter
Armor Class: 2 
Hit Dice: 10
Attacks: 2 Slams (2d6 each)
Saving Throw: 5
Special: Level Drain (1 level); Move Through Stone & Earth
Challenge Level/XP: 12/2,000
Undead earth elementals whose life energy has been replaced by negative energy, so that they are a combination of pure elemental earth plus negative energy (see On the Elements and On the Energies).
Undead earth elementals resemble their non-undead relatives, but are looser in form, being made up of gravel, sand, and silt.
COMBAT: Undead earth elementals are unintelligent and will attack any living creature within 30'. It will continue to attack until it is destroyed, its opponents are destroyed, or its opponents retreat 100' in distance from the undead earth elemental.
LEVEL DRAIN: When an undead earth elemental strikes its opponent, it drains one level from its victim. The victim does get a saving throw and a successful save indicates no level drain. The attempted level drain is limited to once per round, so even if an undead earth elemental successfully strikes an opponent twice, only one level drain attempt is made.
MOVE THROUGH STONE & EARTH: An undead earth elemental may pass through solid stone or earth at the rate of 1. The undead earth elemental may not attack when it is fully or partially passing through stone or earth.