the Blood war

The Blood war  was waged almost entirely by one demon. Terin Demonicus. At the time the Regent of Gahena was his mother , one of the original Fallen,  who had for centuries been using her son as a test subject for the punishments and tortures she would inflict on the damed souls. At the time Gahena was divided into warring factions each with their own "king" who refused to answer to anyone other than Satan. Terins uprising against his mother was a bloody massacre  as he tore through her guards and soldiers , maids, servants , anyone who stood in his way  until eventually he was brandishing his mothers severed head above the ruins of her decimated castle. Dispite their lack of loyalty to the regent, this made him enemy to  all of Gehena, and thus with his one ally Streek, Terin began his bloody crusaid to unify Gahena under his rule by any means necessary. Most factions submitted to him before being completely wiped out and a political marriage ensured the strongest faction was forever loyal to him. The blood shed lasted 1,000 years and would continue in the background for many more untill eventually Terin , through marriage and murder had all 7 embodiments of sin , as well as representatives of every sub species that had survived , in his family consolidating power within his blood line.