[Astromancer]

As a threat/opportunity (and those words belong linked) a real deity set loose in the IW setting is vast. Athena would look for wisdom, Loki would want some fun and playmates, the Mac Og would look for true love, with several thousand women and men. Chaos would ensue. Well not from Athena, much.

Creating a deity who has lost their world and purpose and is looking to find a home and purpose could set up loads of adventures. I'd bring them in first as a whacked out encounter. Then a recurring character. Then they, or the side effects of their arrival, could function like one of Buffy's big bads.