Halderoskar the Infernum
Halderoskar the Infernum was banished to the Elemental Plane of Fire by the gods for a crime lost to the ages. One day, he burst into the material plane and laid waste to all in his path, which at the time happened to be the settlement of the Three Clans. Halderoskar longed for power and knew a shard of great power rested inside the mountain that the Three Clans guarded, so he slaughtered them down to the last man, woman, and child.
To this day, Halderoskar lairs at the mountain, which is now called Emberoskar in memory of his deeds.