The brothers spent a few days in Feathergale Spire recovering and interrogating Thurl. Nothing useful was discovered so they threw or rather let him throw himself off the side of the tower. A split second after a flap of wings brought 5 Aarakocra brothers onto the edge of the building. They had been watching the Spire for a few days, trying to decide whether Thurl was in control or rather being controlled by some darker force, Yan C Bin, the prince of Elemental Air. They gladly joined forces with the brothers and even helped calm the hippogriffs down in the stables as well as teach them a few phrases of Auran. Enough to use them as mounts.
The Aarakocra and brothers both agreed that there was a stronghold farther down the canyon so that night they approached and soon they came upon the entrance to a cave that lead deep into the earth. After a few hours of silent travel they came to a rather large underground stone city. The halls echo with horrible screams and eerie music.
Further in they discovered a tall beautiful pyramid like building that seemed to be the focus of this city. Inside they interrupted the weird worship of a few cult members who were quickly killed. They then ascended the stair quietly in hopes of surprising anyone on the second floor but instead found themselves walking into the throne room of a very tall, very angry looking she-elf with huge wings from her shoulders, Aerisi Kalinoth.
After a bloody fight they defeated her and her minions and searched the rest of the cavern discovering a group of prisoners who were being tortured by a group of kenku. They easily defeated them but Varron took one as prisoner as he recognized some of the screams coming from it. The prisoners knew Desyna but said she had been taken farther down.
The bros then decided to get the heck out taking the prisoners with them. After a long slow journey back they made it to the Spire where everything seemed to be good. They left the prisoners at the Spire and headed back to the cavern to explore it further. They befriended an enslaved djinni and freed him by breaking the horn that bond him to the Material plane. In return he brought them each a Bottle of Breath. He also examined the spear wielded by Aerisi Kalinoth and warned them against using it as he felt a sliver of the dark prince, Yan-C-Bin inside. Exploring further they found a band of air cultist patroling the main temple. They killed most of them, a few escaping by jumping down a shaft going down further then even their elf eyes could see.