Use the following trick to get a powerful spear that has Soul Trap 1,000 points cast when hit. Go to Ald'Ruhn and start looting people's homes on the right side just before you hit Skar, the giant shell thing. In one of the houses (probably the ones that are locked), you will find a blonde woman. Kill her if desired, then go to her bed beside the closet. There will be a spear called Buerketnhgs or something similar. Take it and get a lot of Greater and Grand Soul Gems, as everything you attack gets trapped.