after defeating cereth you're meant to get a screen saying you search the camp, then have a screen discussing what happens, and then one saying you decide to leave and continue exploring.
At that point you can turn in the quest and return to esior's haven.

if you did search the camp, get the next plot clue, and leave, and it isn't letting you turn in the quest, then you'll want to post in bug reports, because sometimes the system in regions 1 & 2 borks up (it's quite old code now and Krin wasn't nearly as experienced so it happens from time to time- you just tell Krin and he'll check and see what happened and set it right if it was a code-bork, or tell you what it is that's going on otherwise)
or you might have just left immediately after beating Cereth and not searched the camp and so not actually completed the quest's plot, that's the other possibility I can think of.

I figured it out, I had to explore the area before I left to the next area (which wasn't there) so I didn't have that but thanks anyway!