asseco - if you release Zlyuka, you will unlock two new parts of the dungeon, although there will be nothing interesting there by the end of the game. Zlyuka should be almost impossible to kill.
But what's the point then?
What I'm getting at is this: there are two separate storylines - Nick and Zlyuka, which are not connected to the main plot in any way. In my opinion, this is not quite right.