You can find a list of hybrids on
You must be registered to see the links
(though I also think the game could make it clearer as to what's what without having to resort to trial and error or looking up outside sources).
For nympho trait to appear, you might need to increase your world level, which requires releasing Nephelym of the same type into the wild. So, to increase e.g. Elf world level, you need to either catch or breed lots of elves, then release them.
IIRC the Risu in Sultry Plateau wants a Seraph, no?