The caster and fighter serpentfolk from the Fortress had teleported away when the morlocks went on their rampage. I placed them at the final fight to add more challenge.
The fighter and huge snake companion were dispatched easily. Vyr Azul and the caster tried to disable/destroy some heroes, but everyone was making their saves... until the caster strode forward and cast prismatic spray.
The druid was sent to Elysium, and the summoner dropped dead from poison...
The cleric was caught in a force cage. The witch flew up and dimension door'd him out. The high priest and caster were finally vanquished. But Ydersius was climbing out of the pit... the alchemist blows his last load of alchemy bombs to weaken him.
The Tempest felt the druid leave the fight and asked their common patron, Gozreh, for assistance. The male and female voices guided the cleric to use the gate scroll on the dead priest's body to call the druid back. the witch began casting raise dead on the summoner.
Ydersius climbs out of the pit, and unleashes his frightful presence. The cleric and the animal companion move to intercept. The druid summoned a celestial purple worm but is blocked by the unholy aura. The cleric and companion, both heavily buffed, manage to cause heavy damage to Ydersius despite his unholy aura, his attempt to turn the companion into a viper, and his blasphemy.
Melee blows continue and Ydersius is taken down without causing any real melee damage to the group. The summoner is finally raised. Eventually they sever his head, sending his thrashing body back into the depths of the chasm from which he crawled, back to where Savith sent him 10000 years before.