This creature is a powerfully built, roughly humanoid-shaped monolith of black stone. Its hands end in wicked, serrated and jagged claws. No facial features can be discerned.
When reduced to 0 or less hit points, an obsidian quasi-elemental explodes in a cloud of razor-sharp bits of obsidian. A creature caught in the area can make a Reflex save for half damage. The save DC is Constitution-based.
A successful hit against an obsidian quasielemental with a piercing or slashing weapon (or piercing or slashing natural attack) that deals damage equal to its current HD opens a wound that spurts molten glass. The wound bleeds for 1d4 rounds and any creature within 5 feet must make a Reflex save or take fire damage from the splash. A new save must be made each round the wound bleeds and a creature is within the area. The save DC is Constitution-based.