Short but still long version.
Party fights some undead dragonlings. Meet a collection of memories of the brass dragon race instilled in memory crystals which grew in this place due to a convergence of leylines nearby. It’s magic, I don’t have to explain shit. They talk about a great dragon war long ago over the dragon orbs and the right to rule dragonkind. Their race, the Brass dragons, were causualties of this war when their home was captured and their dragon orb used to annihilate them.
The party is directed out of the tunnels and finds that the crag that the armored dragon was perched on the night before is a giant fortress floating in a bowl in the canyon, giant boulders floating lazily about it. The party is able to make their way boulder to boulder to enter the fortress which is rather empty save for a evidence of recent archeological work. The party enters a chamber where they can see that a fragment of the brass dragon orb is powering the storm outside. There they meet Brassbane, who turns out to be Astrarian, the copper dragon who had helped the party escape the pyramid. What a Tweest!
After destroying a number of constructs fighting alongside Brassbane, the dragon surrenders, forcefully removing his armor which had been implanted into him with giant spikes. Mind control is assumed to be at work, but Vorastorix doesn’t care, and is about to execute Brassbane when Daelock locks himself and Vor within an illusion to talk things through. Sadly, as the two exit the illusion having decided to at least hear Brassbane’s story, they see Tempest plunging her blade into the dragon killing it. A mercy killing she proclaimed, there was only a small chance that they would have been able to save the dragon anyway.
Daelock has had enough and is about to abandon the party when Vorastorix talks him into staying. The party attempts to rest but they hear voices below. Guards from the Empire have arrived to investigate brassbane’s death and the removal of the brass dragon shard. Using guile and trickery the party escapes and rests in the caves below. A dwarven city resides below Brassbane’s fortress, and from there the party can make their way to the place where Tavar’s raksahsa had been created, the place where Tavar needs components to kill the rakshsaa.
At the city gates the party is confronted by a pair of mean looking constructs. They are just barely able to avoid a fight and are allowed into the abandoned city. Apparently duergar had drove the dwarves out, but then something had drove them out too. The party sees a massive glow off in the distance, and comparing it to the glow from cracks in the ground surmise that it is leyline energy flowing through the ground.
The party finds giant fissure splitting the city in two, a river of energy flowing through it. Bathing in the energy is a giant devil who turns out to be amicably evil and lures a few of the party into bathing in the energy of the leylines with him. The devil directs the party to a nearby library, but when the party begins their way there, realizes what happened the last time they trusted an infernal creature and instead moves to the mines where the party will find a tunnel leading to where they need to go.