Having read all the posts in this thread, it seems to me that you are not using typical pantheons. Thus, almost any deity would do. However, it seems to me that - after the death of their primary deity - the elvish peoples will be quite vengeful towards the orcs. It so happens that (at least in the faerun elven pantheon) that there is an elven deity of vengeance - Shevarash.
Granted, he is the deity of vengeance towards to drow, but 1) surprisingly it seems that there is no deity focused entirely on the (long standing) hatred / vengeance towards orcs, and 2) I can see no reason why he couldn't *also* become the deity associated with vengeance towards orcs, as his portfolio is vengeance in general (and hatred of drow in general). That he is CN also works well, as I can see elves slipping towards 'an eye for an eye' and 'no mercy, no quarter - even towards the women and children' in their lust for vengeance. This is far less of a 'good' behavior but far more acceptable as a 'neutral' behavior and - at times - even 'evil' behavior. Shevarash happens to accept followers of CG, CN, and CE alignments - one of the few non-drow elven deities to accept CE alignments, in fact. (Only two others accept CE followers amongst the elven pantheon - the deity of mischief and rogues: Erevan Ilesere and the deity of outcasts and isolation: Fenmarel Mestarine.)
Having a CN deity take on the leadership of the elven deities, I can see a shift occuring, such that elven typical alignment shifts to CN from CG.
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Why is the Egyptian pantheon without a people? If you are using the Egyptian pantheon, then are you also using the Babylonian / Sumerian pantheon(s)? Exactly which pantheons are you using?
Does the Norse pantheon exist? Much of the flavor of the elven races in D&D was drawn from norse views of elves.
What of the Greek pantheon (which better matches the Chaotic feel of the elves; indeed, the two pantheons exist on the same plane of the great wheel)?
Does the Chinese pantheon exist? What about the pantheon cthulu is a part of? (Just kidding about that last one . . . I hope.)
The main human deities apart from Pelor - do you use the pantheons of Greyhawk (Iuz, etc), Faerun, or some other source(s) for the collection of your deities?
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