Garnfellow
Explorer
I just glanced through my copy of Monster Mythology, and I didn't find so much as an allusion to Orcus's death in either the dark elves section of the introduction to the "Gods of the Underdark" chapter, or in Kiaransalee's write up. I think the idea that she slew Orcus came later, unless there's something I'm forgetting.
Is Orcus even in that book?