The Necromancer is entombed in a tomb under the Temple of Binding separated by a cavern. It appears that the Necromancer’s tomb is more ancient than the Temple of Binding. The party fought through a lot of skeletons and zombies that were unable to enter the Temple of Binding. The tomb contains a sarcophagus that gives the party a sense of unease to be near it. Gaul was somehow affected by the sarcophagus and experienced the not quite entirely dead necromancer’s thoughts and influence.
The Party noticed a swirling portal in the wall. They sealed the sarcophagus of the necromancer with one each of the two types of amulets/holy symbols found in the Temple of Binding. They each “melted” and became thin wires that wrapped around the sarcophagus sealing it tight.
They healed up and then went through the portal and found a mountaintop temple dedicated to The Necromancer. They defeated the skeletons, zombies, and ghouls with their human guards.