The party spent little time with the bodies. Arya sorted through what the mages had carried while Kael looked upward and cast locate object on his missing sword. It was above him, moving slowly, still in someone's hands. Too far to retrieve now.
Tiaumil had a more immediate resource. He had captured the senior mage's soul before it could flee, and he intended to use it. Three questions, cleanly asked. The soul answered with the pride of someone who had worked very hard on something and could not quite resist explaining it. The ritual drew on strong emotions, pain and grief and longing, siphoned through the marble of the tower itself. Two things would meaningfully disrupt it: the elemental rift on this floor, and a prisoner held in the upper laboratories, a deva named Lumalia who had been suffering there for centuries. Kael went very quiet when he heard the name.
Upstairs, they found the tomb of Arcavel the Soulbinder, ringed by four levitating crystals drawing power through the lid. The history Tiaumil and Kael assembled was not reassuring. Arcavel had been the architect of the tower's soul-harvesting systems, a man who believed life was a resource to be spent. He had been multiple souls in one body. He had not died so much as disappeared.
The crystals could be deactivated by password for a minute. Kael stepped forward to move the lid and made the worst roll of his evening. Something in the sarcophagus scanned him, found what it was looking for, and created a copy of him, twisted and wrong, that stepped out of the light wearing his face. They destroyed it. When the party worked out the crystal sequence and finally opened the tomb, what was inside was stranger still: Arcavel's preserved body, and arranged around him like votive offerings, the party's own lost magic items, everything the tower had stripped from them, being used as fuel.
They took everything back. They took the glyph key. They took a short rest. Tiaumil had to talk Kael into using the greater restoration scroll on the paranoia that had taken root in his mind, which took longer than the rest itself.
Then they moved north, triggered a lightning trap, and watched a collared spring eladrin emerge to investigate, disable it without looking troubled, and leave a message on the wall in Druidic before walking calmly back. A shadow-furred rat carried the reply and came back bruised and poisoned with a voice playing out of it. The room ahead was a relaxation chamber with smoke that could be made lethal. The rift was south. The fire was east. The master was bald.
They had what they needed to move.