Attacked Temple of Bane directly.
Appears that being abusive to Orcs before getting to door will allow you into temple unmolested. There is a blind Orc at the doorway who will touch you and unmask you otherwise.
Inside temple, went to altar and destroyed it. Was then attacked by large force of orcs, orc leaders (bows), and leader orc named Mace. Hold Person was able to immobilize Mace before he could cast Hold Person on any fighters. Magic user used Sleep spells to disable large groups of attackers. Then just slogged away at the crowd, and won the battle.
On Mace found a piece of paper:
Journal Entry 25 - Letter from The Boss to priest about attacking Valhingen Graveyard to find source of undead problem.
Finally, in wings of temple (north and south ends) you can find two hidden doors in floor for treasure. Good experience to be had there.