You know he was spying on Erathil? Do you know who he was working for? My information on that is... incomplete...
Either way, seeking such a person out is dangerous at the best of times. When you are seeking out a rather aggressive assassin with the blessing of the god of murder, who has little, if any restraint, when it comes to killing, you had best be careful.
Still. If you happen to meet him, and have the opportunity, don't tell him too much too quickly. Once you lose your value to him alive, he has no reason not to kill you.
So then he goes, YOU SHALL NOT PASS, and I say "I've got WINGS? I can FLY?" It was hilarious! The dwarf was tough, but the elf was delicious and they had some men and these four bite-sized guys, too. The wizard was fuming when I flew off.