The Fallen Ladder
After her Atonment, Vesper met with Penny Escher of the Artificer's guild. They had discovered another Shelter beyond an area called the Fallen Ladder in the underdark. Wan would take them into a radioactive zone so they could explore that shelter.
The party went down to Gambuldar- the dwarven city, where they met Malgoth Fossilmover, who believed the radiation was a death aura caused by an artifact of Zon Kuthon.The party travelled the fallen ladder and found mutated creatures inside. They uncovered a derelict train and saw that the fallen ladder was actually referring to train tracks. Wan repaired the train and went to the area called Station, which was inhabited by the descendants of ancient humans, mutated by their AI, Alexa, to survive the radiation.
They discovered that centuries ago an incident called "The Leak" happened, where Alexa's power cells began to leak radiation. This caused her to lose a great deal of functionality, and most of her systems were shut down. In order to repair it they would need an alternate power supply, either from Shelter, or from a floating city location called Orbit.
They found that they could use Alexa's mutation equipment to protect them from radiation, but the mutations were harsh- Nantar went blind, Wan went deaf, and Kyrian grew a useless third arm. Vesper opted out.
On the end of the train line, Malgoth lay in wait with an ambush, many skeletons, zombies, a few ghast, some shadows, and an antipaladin cohort. Many of the undead were destroyed, but the radiation suts hindered Vesper and Aurelia's spellcasting, Pending was not around, so the party was destroyed by the undead forces in the radioactive tunnels of the Fallen Ladder..