XORN

The xorn are a race of creatures found on the Elemental plane of Earth, but on rare occasions they will abide on the Material plane for a time. When so doing, they seek deep subterranean places. Xorn feed on certain rare minerals which are the subject of their quest on the Material plane.

The xorn is likely to demand such metals as copper, silver, etc. to snack upon, and if a passing creature refuses, the xorn is 90% likely to try to take the metal by force, for it can smell such at 20-ft distance.

The jaws of xorn are very powerful, and as the creature blends with stone — both in color and conformation and as a physical capability — it is very likely to surprise any other creature.

If a combat is going against a xorn, it will stop fighting, adjust its molecular structure, and pass through the nearest stone (usually the floor) to escape. This requires one melee round, and thereafter the xorn can progress at normal movement through solid stone, earth, or similar substances. If it is struck by a phase door spell when in this state a xorn is killed.

These creatures are not harmed by fire or cold-based spells. Electrical attacks, such as lightning bolts, do either one-half or no damage, depending on the saving throw. 

They are flung back 3" and stunned one melee round by a move earth spell, a stone to flesh or rock to mud spell will lower their armor class to 8 for 1 melee round (and the xorn cannot attack during that time as they must adjust their molecules), and a passwall spell delivers 11-20 hit points of damage to the creatures.