From Basic D&D somewhere (no idea where) originally, later updated to 2e in the Mystara MC appendix. They're undead ghost-like things that attack with glowing balls of light that do extra damage against elves and half-elves.
Hmm, I will have to see if I have anything at all to guide me on those...
I might have to leave 'em up to someone else. I had the Mystara MC appendix on loan for a long time, but I believe I returned it about a year ago. I mostly had it for 2e stats on the thoul and, hmm, I think there was something else, but I can't recall what off hand.
What kind of monster collection do you have anyway? Most of the obscure stuff I like to draw upon comes from the 2e MC Annuals, the Mystara appendix (I might skip that if you don't have one), and stuff from older issues of Dragon (mostly late 2e).
Pretty extensive & varied, going back to 1e sources. Generally, if it's pretty obscure, it can't hurt to post the source it's from- odds are I have it, or at least can take a look at a friend's copy.
Ok, I'll list pretty much everything I think is cool.
Fair warning: I think a lot of weird stuff is cool. Prepare for the deluge!