Asa Worldcrusher was an invader from another world. His armies utilized Elven Gates to allow his vast armies to jumping from world to world, universe to universe, to pillag and conquer. He drew upon the resources of a dozen worlds to invade one, after another. His chaotic empire was unstoppable, till he faced the Mad King. Another name lost to time, the Mad King rallied the Peoples of the Flanness, summoned fiends and celestials alike in a desperate bid to slow Asa down. It worked, but, as always, the price was high.
The Elven Gatekeepers had been slain, Asa’s reinforcements denied, his conquest quickly ground to a jerking stop. Asa’s grand empire came to a climactic end, he was killed, his soul given to a Dark Prince. The Mad King barely had time to catch is breath before his own ruined empire choked on civil war. He begged for power, the price his own daughter, one he was to happy to pay. Still, the price was to high, the Mad King was slaughtered for his blaphamy. A few remaining faithful, took their leaders and buried them deep in the earth, each with its own set of unique obstacles and traps.
That was thousands of years ago. Another lost age filled with strange wonder and unknown magics.