I like the idea of the poison being cursed somehow. Perhaps initial damage 1d10 Con, secondary damage a bestow curse spell (-4 to attack rolls, saving throws, skill and ability checks)?

Fair enough point on the elf-shot. So, bestow curse with all the options?
Yeah, I agree with that.Elf-shot for the poison would be thematically appropriate, but elves in D&D aren't very fey. I say stick to "poison".

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.