Umbra' Keth is an entity created by the forces in conflict during the War of Bend'r-Mahk. During 3E 397, it was being sought by multiple parties, including Jagar Tharn and Pergan Asuul, however neither were able to obtain it, and both it and Pergan were eventually defeated inside the Crypt of Hearts by the Soul of Conflict, who wielded the Star Teeth, and was guided by Azra Nightwielder and Skelos Undriel. Its only weakness is the Star Teeth, due to it being an entity of Shadow Magic.
It can be found in the Crypt of Hearts III, where it will use dead bodies to send messages to the Soul of Conflict. Once it is found, it pursues the Hero, even entering different areas. The one area it will not go is the Pool of Safety, which will cure the Hero of any illness. One must then lead the Umbra' Keth to the Vault of the Heavens in Crypt of Hearts II, where they can place the Star Teeth down on their set pedestals. Once this is done the Umbra' Keth becomes vulnerable, and it can finally be defeated.