Glass Doppelganger

Description
This spell forms a living glass creation that is an exact copy of the target with the following exceptions: The creature is made out of glass, and thus more brittle, being summoned in at 1/4 of the current hitpoints of the target. The summoned creature has 15 resistance to fire, cold, electricity, acid, piercing, and slashing damage types. The summoned creature has vulnerability 50% to sonic and bludgeoning damage. The glass copy is allied with the caster, but not under direct control, acting as a summoned animal or a henchman. Creatures copied must have the same or fewer hit dice than the caster has caster levels and no more than 15 HD. Copied creatures have no memorized spells.