I don't suppose you just want to talk?
The city is home to more of those really tough evil mercs, as well as flying strigoi who are fricking tough and have an unbreakable grab attack which depends on a team mate freeing you. Lily almost fell prey to this. The main attraction though was the large demon residing in the grand hall at the end. As the end boss of Bitterblack Isle he has a whole slew of abilities, the scariest of which is one where he banishes people - as he does to Yennefer!
Fortunately we find a new knight ally in the form of Ingvald who is pretty decent as a second tank, but what really kills the demon are a pair of rusty daggers I found, not because of the piss poor damage but because of the slowing debilitation with each strike that connects and as one can imagine, dual wielding daggers usually ends up with a lot of strikes - eventually making the demon move in slow motion. It's pretty epic when we finally slay him.
Turns out he was once Olra's main squeeze, and an arisen to boot - until the dragon offered him a choice which he couldn't decide upon. His uncertainty eventually turned him into a demon, and Olra is pleased that he is now free from his suffering. This doesn't clear the island of monsters though, on the contrary - without the demon around they seem to all have gotten tougher!? Not that it's my problem though - with my task here done we warp back to Gran Soren. I'm now on level 57.