This is the Chaggrin, an elemental grue from the Plane of Earth from the AD&D
Monster Manual II. It spent a long time without spines because I couldn't find the appropriate material. I found a rusty chimney brush in my parents' basement and I knew the grue had found its spines. It still has a vile smell from the epoxy glue, perfect for a hedgehog-like entity with a skeletal head.
The best part is that if you pick it up incorrectly, you might need a tetanus shot.
Illustration of the Chaggrin from the
MMII.