In the underdark there are the three tunnels (East, South, West) where you need to get various monsters' body parts (blood of an elder brain, eyestalk of an elder orb etc) for a drow plot (I forget which). I am an obsessive type of person who wants to raid these tunnels before I enter Ust Natha but, after clearing out the mind flayers' dungeon/tunnel I found no blood on the elder brain (allthough wether it WAS there and I am just deranged is another matter). I want to clear out the tunnels but I also want to play the drow plots. Is it safe to clear out the tunnels and come back later for the blood/eyestalk etc or should I leave one tunnel untill after the drow plot has been given to me?

I also cleared them all before going in the drow city. I did get all 3 items, your problem must be a bug.

But that is not important. You only need to get one of the 3 items. Just go get the kuo toa blood. It know for sure that it will be there. I took it in my latest game, without going in the city before.