...but others have pointed out that in DnD canon lore, apparently vampire spawn go to Mephistopheles regardless, so the only thing that changes is that he gets them a little later and no one gets the powers, if the ritual isn't performed. This ambiguity I think does a big disservice to this overall story.
Well, if the spavn's end up ending up at Mephistopheles anyway, then I don't see a moral dilemma with getting the power at all... And I apparently haven't learned anything, since every pass the spavens are sent to their destination...
