The Robert J. Schwalb 4e lore for the "shadow of the void" wraith and the "shape of fire" wraith include the following passage:
>The shadows of the void and the shapes of fire are peculiar wraths found in the starry realm of the Astral Sea and are products of Nerull’s dark designs. To feed the dark god’s ambitions, he annihilated entire worlds, his angels flinging their screaming forms into the stars to be consumed and their soul energy extracted to feed his rapacious appetites. So evil were these genocides, darkness infected the dead’s spirits and thus were born these most deadly of all wraiths.
In other words, these are wraiths born from worlds hurled directly into suns, which is insane.
What are some other off-beat undead you are fond of? Atropals, stillborn god-fetuses, and Atropus, the undead moonlet-head of the Prime Mover, tend to be popular specimens of weird undead.
>>54072496
I can't find any source for those in 4e. Are you sure it wasn't 3e?
More to the question, an idea I like and want to expand on is 'larvae' - evil souls who return from death in masked, insectile forms.
>>54074785
This is quasi-official conversion work from Robert J. Schwalb's project to convert Epic Level Handbook monsters to 4e.
Well, there's those hobgoblin undead that liquefy living bones and suck them out of people. Then you have the skins of people that come back to unlife and skin people alive.
Lemme think, fuckin uhhhh, there's also shadows. I always liked shadows; in Pathfinder they give templates like the jungle shadow, which can be shaped like a bat and always causes its victims to become jungle shadows.
>>54074785
Larvae are outsiders, not undead.
>>54072496
I've always had a fondness for these.
>>54077624
http://archives.nd.edu/cgi-bin/wordz.pl?keyword=larva