It's more than that, the final act felt unnecessary to me, you defeated the actual villain of the story and suddenly some foreigners appear and tell you to go to their lands to help them, you have no reason to help them, and no real reward is offered, but you're also not offered any option to at least show some doubts about the request (Especially if you're evil, what the hell), after helping them, you're blamed for a lot of things and then forced to keep helping (and you don't have the option to... say, kill the messenger on the spot, since you're in your castle and it's not like they can touch you, right?)
The act was rushed, added little to the story, the final boss was someone that came out of nowhere with no foreshadowing, simply grabbing whatever was left of the previous villain. The final act could've worked as an expansion, or as a sequel, but it was part of the main story.
IMO, changing the twists would've worked a bit better, like having the previous villain resurrecting himself by possessing suitable vessels, and trying to corrupt the PC, since they were shown to be perfectly capable of defeating it.
Quality of writing is often a serious issue in western adult games, Adorevia is not exception to that, and sadly, they focus more on adding new content, rather than revising badly written scenes and fix them.