How about a trickster, Anansi..specifically. He is mentioned in one of the books...but it doesn't look like there's much backstory to him otherwise and I don't see a mention in the series. He would have the same type of powers as Gabriel/Loki, but he's much more serious in tone and actions. He only really kills murderers and people who commit atrocious crimes, but will definitely wield his power to trick someone if they cross him or try to get into a pissing contest with him. Working on some backstory now, let me know if that sounds kosher!