Robbing the Dead

Been thinking of things we could do to walk away from the big nasty lich in one piece. Toe to Toe combat isn'nt going to be the most ideal situtation, and I don't fancy becomming maggot food. So things I thought so far.
1) pretend to be worshippers of bane and negotiate for the light stone and maybe the elven maiden.
2) Work out a way to bury the lich for good, so no one can ever enter this area. If we can produce earth in mass quantitywe could fill the chamber so the ground dos'nt collapse from above. Within the earth if we mix if with white stone this could slow down or stop magical digging. and maybe we could seal the door with stone and collapse the stair wells in the tower. If we explain to the lich that it will come to a point when the ground above will collapse, he have endless mortals travelling down there he will never get any sleep. could be enough reason to stop him from smashing our skulls in