After fighting their way through the pass (that chapter 2 map was not even a quarter of its true size; looking at it now it would have been quite the slog), the party reaches the dwarven bank only to discover that a group of wasteland bandits has taken residence. After fighting their way in, they explore the bank until they find Zelda's family vault. The find the Mask of Kings inside, but something is wrong: not only is it not nearly as ancient as Zelda's story made it seem, but it is quite clearly of human design rather than dwarven.
Zelda reveals that the mask was actually created by her father, using forbidden magic, in the hopes of overthrowing the Empress and ruling the Empire himself. She first brags about how her fiance will become the most powerful man in the world, then uses the mask's power (mind control and minor teleportation) to betray the party and leave them for dead while a group of monsters attack. After defeating them, Porkins will suggest trying to reach Duke Eastland and warning him that his younger brother is not only dealing with nasty magic and insane women, but is quite clearly attempting to go traitor. The hope is that the Duke will honor his younger brother's deal with the party in reward for warning and possibly fighting for him.
If the party decides not to do this, the campaign switches to Plot B.
Should the party decide to warn Duke Eastland, they begin making their way south, skirting the mountains in order to try and avoid enemies. This, predictably, fails. They discover that a substantial wasteland force has gathered in northern Montaga. That would be bad enough on its own, but they've also managed to make some sort of agreement with one or more dwarven clans, and those dwarves are providing both cannons and the operators to run them. If all that wasn't bad enough, the wastelanders are marching south, presumably on their way to Castle Eastland to meet up with the enemy garrison.
The option is given to either sneak around the slow-moving army, or to try and destroy the cannons. Sneaking around gives the party a stealth segment followed by a timed escape objective when they are inevitably discovered by the army's scouts. Destroying the cannons involves either a nigh-suicidal charge into the heart of the wastelander army OR luring a nearby dragon into the wastelander force and letting it go to town on the cannoneers instead. No matter which path the party chooses, they reach Castle Eastland - and the Duke's army - before the wastelanders do.
The party is granted an audience with the Duke, who is skeptical about their stories. However, he is grateful for the warning about incoming enemy reinforcements, and so makes the team an offer: help him retake the castle, and he'll consider honoring his brother's agreement.
The party has a choice between accepting, or refusing and getting locked up. If locked up, the party swiftly breaks out and the campaign goes to Plot B.
Shortly after the battle for the castle begins, wastelander reinforcements will show up. If the party had not destroyed the cannons, the enemy dwarves set up and begin firing. Some time after that, the General shows up with his own army. He directs his mind-controlled soldiers to attack both the Duke's forces and the wastelanders, who by this point have substantially weakened each other. The party is directed to sneak around the three-way melee and attack the General from behind, where he is only lightly guarded. Zelda is there, but she flees if she takes too much damage. When the party kills General Eastland, the mask explodes and his soldiers regain their senses. The wastelanders are swiftly routed.
The party is wounded in the magical blast, and are captured by Duke Eastland's personal guards. When the team recovers, Eastland reveals that he did indeed have his healers remove their brands...only to dose them with magical poison instead. The poison remains inactive as long as a special antidote is taken once per week. You see, the party did so well, impressed the Duke so thoroughly, that he's decided that your talents are too good to let go. You now work for him, and what's more now you can be used in public without fear that you'll be executed because you forgot to wear gloves.
After that, a timeskip of roughly two months. Most if not all of the party will be promoted during this time frame - trained exhaustively by the Duke's men. Eastland assembles the party one day and tells them that there is trouble in Toulouse. The constantly-feuding nobles there have started engaging in active rebellion and anarchy. Forbidden magic is running rampant. The Empress has called on many of her dukes to provide soldiers in an attempt to squash the unrest. Accompanied by the party and a small squad of normal soldiers, Eastland travels to Toulouse in response. They meet the Empress herself (indirectly, of course; she's far too busy to talk to a bunch of common footsoldiers) and some of her top advisors.
During a battle against some deranged cultists, the Empress is critically wounded by an unknown spell. She is quickly removed from the battlefield and most of the allied forces follow her. Eastland and the party are instead captured by none other than Zagathax; Abih's chief mage, who had been thought killed in the final climactic battle the previous year. It is revealed that the Zagathax who died was actually a doppelganger produced via blood magic. What's more, Abih himself was a construct of Zagathax's making. The mage was the true mastermind and power behind the invasion all along.
While Zagathax is annoyed that the Empress has once again escaped death, he sees a unique opportunity in the capture of the party. He offers them a deal: kill the Empress, and he will cure the poison that the convicts are bound with. Specifically, he wants the Empress killed with a powerful potion that he provides, one that will bring the Empress back from the dead as a Revenant under his direct control.
This next part...well, this would require some creative thinking on your guys' part. You would have to decide whether or not to follow Zagathax's directive, and how to go about it. There would be three broad outcomes:
1) You follow Zagathax's orders and kill the Empress, who is still recovering from the spell she was hit with. When you return to the mage, he reneges on his deal and attempts to have you sacrificed to produce a newer, even more powerful version of Abih. He's incredibly tough (more on that in the next section) and has substantial forces behind him, so you're not remotely guaranteed to win. If Zaggy dies, the Empire is in piss-poor shape from the loss of the Empress and the party is likely to remain in bondage to Duke Eastland for the rest of their lives. If Zaggy wins, the Empire's basically doomed.
2) Through honesty or trickery or both, you make Imperial forces aware of Zaggy's existence and ensure that they are willing to commit forces against him. When assaulting Zaggy's hideout, the party discovers that Zaggy is no longer human, but a Lich. He can't be killed unless the orbs containing his life force are destroyed. Luckily the Imperial soldiers are distracting most of Zaggy's forces, so the party actually has a chance of first destroying the orbs then killing Zaggy once and for all. Afterwards, Eastland cures the poison for real and the party receives pardons and rewards from the Empress herself. This is the Good Ending.
3) The party fails/decides not to either kill the Empress or convince Imperial forces of the danger brewing. They die when the antidote wears off and the poison finishes them. Mission Failed.