So the players arrived at Red Larch and collected some information. They already knew about the tower of the air cult, but now they could see its location and find out that the locals thought it was just a hunting lodge for young knights from Waterdeep who liked aerial mounts. From the Order of the Gauntlet contact they got the information that a dwarven history book like the ones transported by the missing delegation had been seen in Womford. And a shephard in the tavern gave them the information that he had seen fresh graves south of Sumber Hills.
The whole role-playing from Phandalin to Red Larch took quite some time, but in the end the group decided to head towards the fresh graves and check them out, and to go towards the air cult tower from there. In the graves they found two dead members of the Mirabar delegation, as well as two different cultists, one of which they could recognize as an air cultist. While wondering who had buried them and closing the graves again, they were attacked by air cultists on giant vultures.
The encounter as written in the book wasn’t dramatic enough for my taste, so I had added a fourth air cultist as well as some helpful Aarakocra. But as the giant vultures by themselves were already rather strong, this made the fight rather tough, with several people having to made death saving throws before being healed by their friends. But in the end all went well. Their new Aarakocra allies explained to them that they could approach Feathergale Spire either from the top, but there was a drawbridge, or from the bottom through Sighing Valley. The group preferred the stealthy approach to knocking at the front door, and so I know what to prepare for the next session.