I went through Venture Cave three times (having defeated it only once before, with a Rogue class) for this quest - Fighter, Berserker, Warlord. Didn't pick up on the Elf requirement for the quest, so I did it with Orcs for the first two and a Gnome for the third. Finished my run of three, didn't get the quest fulfilment, went "WTF?", and checked the requirement. Oops, elves? Okay, guess I need to run it three more times. So I played through with an Elf Fighter... and got the fulfilment.
Expected: I would need to rerun twice more (with Elf Berserker and Elf Warlord) before getting the quest fulfilled.