It'll be a bit hard, seeing as the assassin's strength is in backstabbing, and a dragon can't be backstabbed. Still, it *can* be done - depends on what level you are and what weapons you have at your disposal. Are you soloing? That's going to make things a bit more difficult.
I'm afraid that the Pixie Prick is a bit too small to take him down though. You might need something a bit...bigger.
