Drakensang is a pretty cool game that I was enjoying very much, Kieron favorably compared it to playing a game of D&D with your pals (so both great, and not great under other aspects, as you were saying) …up to the “rats in the cellar” quest.
The designers thought cool to play a prank on players and added a final boss area that’s bastard hard and cannot be left unless the boss is beaten. While I don’t recall the specifics, the long and the short of it, is that unless your party is a certain level, you probably can’t win. Certain party comps may also have a harder time than others.
As part of the prank, the dungeon leading to the boss room is also quite large, and the rats are wolf rats, so that took a toll on my party.
Crucially, it left me with no good saves to go back to. It’s a difficulty spike that came completely out of the blue, as you noted, too, the encounters had been very manageable, and one that culminated in the boss.
After many, many tries, I gave up entirely. If you haven’t taken that quest yet, make sure you go in prepared.
BTW I also remember complaints that the late game gets unreasonably hard and frustrating to play, YMMV.
I would have loved to keep exploring the game world, as it was giving me that warm fuzzy feeling, with its D&D P&P campaign flavor. The prank however seemed just so idiotic and mean spirited, that it robbed the game clean of any trust and promise it had previously built.