Aboleth was a mind reading and mind speaking fish in a tank in the Drow city of Ust Natha. As it was in a tank and always stationary, it had a Duergar slave to work for it.

After rescuing Phaere from the Illithid, Aboleth's duergar slave will approach you and ask you to speak with its master. The fish will ask you to enter Qilue's home, kill her and take her brain. You can either refuse to do this for 12,000 xp, or complete the task for 10,000 xp. If you complete it you will also get xp from the dead drow as well as the Boneblade +4 dagger.