Tol Kharash, the Horned King, is one of the Overlords who ruled over all of Eberron during the Age of Demons. The Horned King was bound by the dragons and couatl after they jointly discovered the Draconic Prophecy, and the couatl sacrificed themselves to form the Silver Flame.
Much like Rak Tulkhesh, Tol Kharash is a spirit of war, but the Horned King is less concerned with the war itself and more so with the aftermath. The Horned King is an overlord of tyranny and oppression, feeding on the suffering of those who have been conquered, and on the cruelty of those subjugating others. In particular, Tol Kharash delights when mortals inflict suffering on their kin.