They were the masters, and overlords of all the races. Then, the power of the races were realized.
The Bomb detonated killing all races. The Ash and dust of the remnants rose up from the dirt and the races were ressurected. Because of the skeleton's extreme power, it would take a while for them to be revived. An elven scholar, "Victre" predicted that one day, the skeletons would rise once again, and exact revenge on the races once more. Little did he know... he was onto something.