In the end of it i met a dragon with some silly name i can't even remember that gave me a quest, killing his naga enemy in the Temple of Creation.
So i went there, and after lots of saves reloading

Last room that had plenty of naga and the target of the quest, Slasul.
Slasul ran to me while i was backing the hell out of that death trap and went around a corner (remembering what a naga gang can do in 1 or 2 turn) and instead of fighting, he explained me that the dragon was the bad guy and lied to me.
Nice, an alternate branch for the ending of that quest.
So instead of trying to kill Slasul, i accepted to get back to the dragon and ask him about his lies.
Slasul created a portal and told me to step in it to get back to the dragon.
That sounded nice, but ...
He created the portal back into the room, while a few seconds walk is not a problem, what was a real one is that the bunch of naga that were following Slasul and me were always hostile to me, and they were shooting through like crazy.
And Slasul while apparently not hostile was always running into me, triggering the dialogue again and again and ...
dialogue in which my only 2 choices were "attack" or "Farewell Slasul".
I had fortunately a save from before entering the room, but this problem always happen, there is no way for me to reach the portal Slasul opened without killing both Slasul and the bunch of Nagas following him.
I guess that's not supposed to happen like this and is very likely a bug, but is there a solution that would not screw up the quest in any ways ?