Berserkers

Berserkers are men who wear the skins/bones of bears within the Teen Wolf Universe.

According to Chris Argent, Berserkers don't just wear the bear parts to channel the animal's ferocity, they actually become animals themselves.

Argent says their human side doesn't last long because they are not tempered by the moon.

Based on the two Berserker deaths shown: the body turns to dust at the moment of death suggesting they were no longer human.