Sul Khatesh, the Keeper of Secrets, is one of the Overlords who ruled over all of Eberron during the Age of Demons. She was bound by the dragons and couatl after they jointly discovered the Draconic Prophecy, and the couatl sacrificed themselves to form the Silver Flame.
Sul Khatesh claims mastery over magic, the arcane, and secret knowledge of all kinds. She is one of the Overlords that is most likely to create Warlocks, as her power is dependent on the practice of magic, and the spread of secrets. She is bound beneath Aundair, in the region surrounding the village of Arcanix.
Sul Khatesh is said to touch mortal minds even while bound by the Silver Flame. She might have influenced the wizards of the Arcane Congress, or had a hand in driving Mordain the Fleshweaver down his dark path. Regardless of the truth of this, the area around Arcanix is magically potent, and many wizards have had arcane breakthroughs there.