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From Pathfinder Impossible Magic, which isn't enabled.

Crystal Lattice

ITEM 12
Price 1900 gp
Bulk L
Category unarmored
Group cloth
AC Bonus +0
Dex Cap +5

This +2 resilient raiment explorer's clothing is a longline vest made of a flexible, durable lattice of many fine crystals. A wide variety of these vests exist, and their colors depend on the type of crystal that forms the lattice. The crystals glow briefly when an enemy hits the wearer.

Activate—Crystal Exoskeleton (concentrate, manipulate)
Frequency once per day

Effect The crystals on your vest grow and extend, becoming an architecturally sculpted exoskeleton that covers your form. You gain 20 temporary Hit Points that last for 1 hour. The exoskeleton crumbles into dust when the temporary Hit Points are depleted or when the duration ends, and the crystals return to their original state.

Effect: Crystal Lattice

Pathfinder Impossible MagicORC