Umm, he's fighting the lich in the Fields of Slaughter; he hasn't made it to the Severed Hand yet
One thing you can try is this: have someone with improved invis grab the holy water and make a run to the waterfall. Dropping the holy water in there will kill all the undead in the fields. If you have a mage with Antimagic Field, use that person as a distraction (the only danger is if the lich uses Banshee Wail; that goes through for some reason). This is the fastest way of cleaning out the place without a lot of fighting.
Nightowl2