The lich in the docks (the tactics one
) is pretty easy and gives up a scroll of timestop, which can be useful early on.
I suggest you try a few TRIAL runs against him in a less vital game first, because his friendly skeleton warriors and the boner golem (hehehe) can be a little tricky if you arent the greatest tank in the world.
TIP: Invisibility.
Good luck with it matey.