Just to sum up events:
After a night hiding in the ancient dwarven city, the party is attacked by some sort of invisible creature. It’s a tough battle, but they drive it off.
The party then returns to where the air cult is headquartered, almost immediately get into a large battle with human cultists and kenku armed with bows. Again, it’s a tough battle, but the party manages to overcome their enemies. Unfortunately, they are left in a greatly weakened state, with Organnac being forced to carry out the unconscious forms of Javonte & Nasim while Silveno guards the strategic withdrawal.
They return to their previous camp site, only to be attacked once again by the invisible creature. Organnac is knocked out quickly, so Silveno attempts to flee. The creatures dogs his heels the entire time. Silveno manages to make is back across the rickety bridge, but ends up falling off the stairs, only to be caught by a wyvern and its rider. Deciding surrender is the best option, Silveno relents.
The whole party is brought before Aerisi Kalinoth, leader of the air cult. She is quite angry, and starts off the conversation by grievously wounding Javante with a lightning bolt, though he is allowed to live. She denies claims that her cult has anything to do with the valley’s troubles, claiming it is the work to the Cult of Black Earth. She agrees to let the party go if they are willing to make amends by destroying the Cult of Black Earth, which the party agrees to readily.
With that, they are marched back to the surface by the kenku and one of the cult’s spellcasters. As they limp their way out of the canyon, they come across the imposing figure of Maluth Clanguard Caragavi. After a somewhat tense introduction, it becomes clear that the goliath is no danger to them, and he agrees to help them in their quest.
Heading off to the Sacred Stone Monastery, said to the the headquarters of the Cult of Black Earth, stories are shared and wounds are recovered. Along the way they find a quartet of shallow graves, which contains the remains of a dwarven artisan, a soldier from Mirabar, a warrior wearing strange stone armor and a body that clearly belongs to the air cult the party just left behind. Maluth insists on giving the bodies a better buriel, so the party settles down for a while to take care of it.
After a couple of days travel, they finally find the Sacred Stone Monastery. Nasim fails miserably to convince the monks of the monastery that they are members of the cult, and a battle breaks out. They are jumped by several monks, as well as a priest of some sort and two warriors wearing that same stone armor. It isn’t long before a half-dozen grey-skinned dwarves also join the fray.
After a long, brutal fight that the party barely manages to win, they retreat from the monastery to lick their wounds before reinforcements can overwhelm them. They flee the hills out into the plains several miles, eventually setting up camp once they are convinced that their enemies are not pursuing them.