Angels of Tartarus

In his quest for freedom, Azrael renounced the sanctity of the higher planes, became the first dark angel, and built an infernal kingdom where achievement and glory trump all else. Thousands of years after his death, discover the Nephilim, angelic inheritors of his lofty dreams and terrible temper. 

In the name of Triumph, the Tower of Babel stands like an arrow shafted through the heart of the Astral Sea, jutting from the lower planes, and threatening the cosmos entire with annihilation if they stand in the way of the Angels of Tartarus.