The rat nest ending

[Letsplayforfun]

I was possessing my familiar, while my summon killed the rat, and then could not end the quest.

[Thomas_Not_very_wise]

Quest endings are based on the Character tool each PC has...

Your familiar doesn't have it.

[ScottyB]

Not much we can do about this, I think, due to how NWN treats possessed familiars.