All ends with a Sharknado
As Three Weeping Ravens just fused with Balance, the team first assumes that someone could have been after the Trillith. But neither the Ragesians (who are about to pack up and return to Sindaire) nor the people of Eresh have seen their missing companion. So they decide to search the village for signs of combat and get lucky.
Near one of the shrines Tinuviel spots some traces of blood and marks of a battle between a humanoid and some rather unnatural beings. The also find some grinding marks nearby and decide to follow that trail. After a while they spot something really unusual: Three Weeping Ravens is floating in midair and being carried towards the mountain pass leading to the hidden valley. However, no one seems to be carrying him.
Cuin'halar uses a quick see invisible spell to discern what's going on as two invisible stalkers seem to have taken their comrade captive. They decide to intervene and one short fight later it is one of the two stalkers who is made captive. They question the beast and find out that the two of them were summoned by none less than Cai Lei Wsu.
They remember the vision Crystin had quite a while ago and instantly link the clawed Stalker, the “wintry song of agony” and the “deceptive East Wind”, as well as “Three Weeping Ravens lead to treacherous wings, yet Balance lives on” to Pilus' student who tried to kidnap their friend. Then Cuin remembers that Eril said something about his group (and some townspeople) disappearing and it seems like they've found their culprit.
So they do what they do best and... head to the monastery to tell the monks about Caela's crimes. This time, a friendly monk awaits them at the gate. He is shocked to see them reveal the invisible stalker with some pigments (the Stalker wasn't amused...) and has no real reason to doubt their story when the creature confesses the name of its master. As they find out that Caela is actually one of Pilus' highest ranking students, they politely ask if they can get an audience with the monastery's masters to deliver the creature to them.
They are led through the marvelous structure only to find the two brothers in a pretty humble meditation room. Both seem to be curious why these outsiders have come to see them and they explain both Pilus and Longinus that while they've originally came to look for their missing friends and maybe get help in terms of the firestorm in Sindaire, they now have reason to believe that Cai Lei Wsu has been abducting people from Eresh for quite a while now.
Both masters appear to be shocked by this revelation, but the Stalker poses enough of an evidence to believe the group. Longinus explains that Cai Lei Wsu is primarily Pilus' disciple, so it'd fall to him to punish her. Pilus muses that she could have gone to the forbidden valley of Storms where he originally conducted biomantic research for the Khagan. He left his old laboratory unattended for quite a while, but maybe his student seized the chance to do some research for herself. He adds that he'll take care to punish Caela once she returns, but if they wanted to speed things up, they could go into the valley and catch her for him.
Note: Ouch. Didn't anticipate that they would actually take the invisible stalker prisoner. And who'd have guessed that they would drag him to the monastery and tell Pilus and Longinus of Caela's crimes? So I had to change things on the fly. Pilus took a bit of a gambit here as he basically sacrificed Caela to let her take all the blame for what happened in the lab. Plus there was that not so small chance that his master student (or the biomantic creations. Or the traps) would actually defeat the nosy outsiders.
Before they eventually take the bait and head to the forbidden valley, the team finally asks what could have caused the storm over Seaquen as the magic seems to be directly related to what they've witnessed here and Eril said something like that as well.
Longinus then stares at his brother for a while who takes a long sigh and apologizes. He explains that he didn't know his student Lee would actually let the situation escalate that dramatically. However, he is no friend of the Ragesians (otherwise they wouldn't have besieged Eresh) and faked an alliance with Leska to gain information from her. When he saw what happened to Seaquen, he quit the matter though and realized it was a mistake.
The party and especially Torrent is rather shocked about this blunt revelation. They explain that Lee Sidoneth would have rather died than to reveal information about his master, so there must have been some kind of radicalism and devotion to the monk. Torrent also adds that Lee had changed a lot since she last met him and that he had some kind of fatalism she'd never seen in him.
Pilus says that he's sorry it ended this way for Lee. But sometimes sacrifices have to be made in order to ensure a lasting peace. Cuin asks Pilus how they should ever trust them if they could just switch sides whenever they deem “peace” would be achieved easier with the other side. Longinus tries to step in for his brother, but Pilus' otherwise very serene face turns bitter as he tells them the story of their home town which was obliterated by the Ragesians years ago. The master of the west wind adds that he'd never ally with those who killed his friends and family and even if balance is the easiest way to find peace, Leska has to be brought down once and for all no matter the cost.
With an uneasy feeling the group departs from the monastery to search for Caela in the forbidden valley. Longinus and Pilus made sure to give them a token they could show to the wardens of the valley so they would be able to pass without hindrance.
Note: And this is how they avoided the defenders of the sacred valley encounter. The monks knew nothing of all the biomancy going on, so Pilus wouldn't waste his own people and not telling the party of the wardens would have raised more questions...
As they reach the higher regions of the valley, the team is shrouded by deep mist. This is when they hear the dread wailing of the valley of storm Ettins. When the group gets close enough to actually see them, they immediately attack the intruders. Tinuviel advises Crystin to take cover somewhere safe and the other four team up on the Ettins. They fell them one by one but not without taking some damage. Cuin says he's sorry for the poor creatures who are clearly the product of a biomantic mishap. He remembers Dogwood's research and finds that biomancy is a terrible art in the hands of the wrong person.
Then they see a large tower near the end of the valley of storms. Pilus gave them no description of his lab, so they just assume that this structure has to be the one they are looking for. However, they are quite a bit curious why anyone would leave the damn thing undefended. Tinuviel is the first one to head towards the tower and the first one to fall to the illusory tower. He manages to avoid falling to his icy doom and sees a strange amalgamation of flesh, as well as some nasty spikes at the bottom of the pit.
A closer examination reveals that there might be an entrance down the pit as well, so they climb down and fight the four mishaps who pose no real threat to them. However, they are shocked to see that the creatures could have been formed from what might once have been the other members of Eril's party. Cuin muses that they might have been too inquisitive and Cai Lei Wsu silenced them before they could find out more about her deeds.
Unfortunately, they trigger the chain lightning trap and Tinuviel intervenes heroically to take the lightning strike aimed at Crystin (he has evasion and dodged his own spell, so I allowed him to take full damage for his “daughter”). He asks her to take cover once they get inside as he doesn't want her to get hurt.
The group slowly and carefully searches for clues in the seemingly abandoned lab. They find numerous biomantic tanks, but most of them are empty and they cannot make any sense of the inscriptions. Then they notice the presence of... something. Or someone.
Cuin and Tinuviel agree to proceed slowly on one of the bridges when they are suddenly charged by Aurus, the Air-taurus (A minotaur is called Minotaurus in German, so it makes a good pun there). He hammers Tinuviel and the elf quickly realizes that this creature is not very susceptible to his attacks. When Aurus prepares to do an overwhelming charge however, Cuin parrys the hammer swing and stops him which... leads to a quick end for this foe as he loses his elemental qualities and becomes an easy prey.
Note: I had to make a quick rule on what happened when Aurus' hammer was stopped by Cuin's scimitar. He did strike him but Cuin wasn't knocked down, so his movement ended right before Cuin where he became dazed and lost his DR.
After Aurus' defeat they continue to search the lab for signs of Cai Lei Wsu. They don't find her at first, but stumble across a giant basin filled with a bit of biomantic fluid. This is where they get really, really frightened. Cuin and Tinuviel take some time to exchange thoughts about what giant creature Caela or Pilus might have grown in there and where that thing might be right now. They just hope it isn't with the missing student.
Last but not least they find the entrance to Pilus' study. Tinuviel tries to sneak in, unaware that they already triggered the silent alarm when they first entered the lab. To his surprise he is attacked by a magical rug which tries to entangle him. Tinu is quick enough to avoid being swept under the rug though.
Cuin, Torrent and Three Weeping Ravens rush to Tinu's help and see Cai Lei Wsu floating in midair. The woman has clearly expected them as she is surrounded by lightning and looks quite amused. “You surely don't understand what 'forbidden' valley means” she says and adds “Well, at least you defeated these annoying Ragesians and sent them back to the stables where they belong”
“You'll be going down for what you did and it won't be the nice way of 'going down'” Cuin replies and jumps at the floating sorcerer-monk.
Cai Lei Wsu instantly responds with a quick combination of lightning and fist-weaving. Unfortunately for her, Cuin is the quicker one to act and so he parries her blows quite easily.
“Sorry dear, lightning's
my specialty” he says and unleashes a full barrage of lightning enhanced scimitar slashes at her. Then Tinu stabs her from behind, sealing the monk's fate.
Note: I really thought Caela would pose more of a threat to them as I made her a monk-magus gestalt (which is a damn fine combination by itself). Never underestimate the power of initiative when you're going against a parry-happy swashbuckler. Did I already mention that NPC have way too little HP in Pathfinder?
Torrent makes sure to stabilize Cai as they promised to return her to Pilus. Then suddenly all hell breaks loose when a lightning strikes through the skylight in the study and strong winds enter the laboratory. The party muses that maybe something or somebody could have enraged the spirits of the forbidden valley. While they think about hiding underground for a while, this plan seems to become more and more dangerous every minute. So they run back to the entrance while everything in the lab is slowly smashed into rubble by violent winds.
After they get out of the pit trap, they run down the valley and avoid small avalanches going off here and there. After a while they find a cliff to hide underneath and cuddle up. Once the winds die off, they suddenly spot something in the sky. Something that cannot be. Or at least should not be. Far above them, a gigantic, shark-like creature appears, even if only for a moment. But what's even more disturbing is that this creature had one damn big eye at its belly. And it was watching them.