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Is there much precedent for demonic/daemonic/lesser extra-planar beings?Aside from Domination entities, you also have Dendaran spirits, Efreeti and Water Sprites, all of which are extra-planar.
I know there's demons in the Vortex (which I haven't gotten around to looking at yet), but I can find little information beyond the chaos planes for Domination, and information concerning Azvosh and the earthen.
The help file on Yggdrasil mentions the infernal planes, but I can't find anything beyond that, and I suspect that that may just be a legacy help file.