Corebros

Bestiary Description
Spike: Corebros are "magically attuned and aware elementals, comprised of sustainable magical gems acting as a core for their jagged, piercing rock exterior." They're commonly found in rock fields and caves, since they spend pretty much all of their time digging for gems. They need gems to keep them going. Kind of like me! They're pretty mysterious, and no one really knows where they came from. They're just kind of there. They generally leave ponies (and dragons) alone unless threatened. But you three actually managed to fight one, huh? Wow! They're resistant to fire since they're made of rock, so I guess Twilight must've used ice on the one you fought. Corebros also have gem-based tools growing out of them that can be used as weapons. On one arm there's usually a drill, used for tunnelling. Legends say that the drills have so much magic power that they can "pierce the very heavens themselves." And on the other arm there's usually a blade used to cut gems. Even diamonds! Man, if I had arms like that, I could just go out and dig up gems to eat anytime I wanted! That'd be pretty awesome.