Luckily my current character uses different ones.

Anyway, it really doesn't matter what race you go for assassin. They all work, just differently.

I personally am happy to play human and use flight potions, but it does make assassinating harder as using a potion is not lag free. Therefore arial might suit you better. Arial however, has nasty vulns and sucky hp.

Felar are perhaps the best if you go villager. Drow permasneak is good. For example, my death to Odonomus would not have happened if I was drow, because they can start sneaking before fearie fire wears off, and that would have let me double back safely. Likewise elf, who also have some nice daggers available that exploit duergar, orc, and mages.

Really it is up to you. Raw physical combat, felar. Assassination and non-mage combat, arial. All rounder, human. etc.

Incidentally, I don't think that many assassins could get that item, even at hero. Having nice healing gear helped a lot.