Tiamat

Tiamat is the serpent-goddess of chaos, not much is known about her besides the fact that her power was channeled by priests into a magical cursed coin with her image carved into it that also was named after her.

Powers and Abilities

 * Power Granting - Babylonian priests were able to channel Tiamat's chaotic power to make a cursed coin.
 * Reality Warping - The coin had the ability to grant wishes, but in a way that they always ended up badly.

Appearances

 * Season 4
 * Wishful Thinking

Trivia

 * Tiamat is the first deity to be mentioned in the description of a magic object related to him without really appearing on screen, the second is Hesperus when Beau was describing the Amulet of Hesperus, and the third is Thor when Beau was describing the Mjolnir, both in the same episode.