This creature appears to be a man-sized humanoid composed of smoothly-formed rock. Its features are human-like though emotionless.
Speed 30 ft., burrow 20 ft.
Str 17, Dex 12, Con 15, Int 10, Wis 11, Cha 10
A lythic can use its Stealth skill even when being observed. As long as it's within 10 feet of some sort of stone, a lythic can hide itself from view in the open without anything to actually hide behind.
A lythic can glide through stone, dirt or almost any other sort of earth except metal as easily as a fish swims through water. Its burrowing leaves behind no tunnel or hole, nor does it create any ripple or other signs of its presence. A move earth spell cast on an area containing a burrowing lythic flings the lythic back 30 feet, stunning the creature for 1 round unless it succeeds on a DC 15 Fortitude save.
Anytime a lythic suffers more than 50% of its normal hit points in damage in a single encounter, it flies into a berserker-like rage. This grants the lythic a bonus to its damage rolls equal to one-half its Hit Dice for the remainder of the encounter. It cannot end this fury voluntarily but continues until all opponents are defeated or have fled.