Schlumpsha the Sewer King is a slime encountered in the sewers beneath Baldur's Gate, surrounded by other unpleasant creatures. Unlike other members of its species, it is capable of speech, and comments on how it has heard of Gorion's Ward and their exploits. It is possible to kill Schlumpsha after choosing certain dialogue options, though one may also cause it to leave peacefully if you don't provoke him into fighting.
The sewerfolks are worth 1575 exp and Schlumpsha is worth 2500 exp. Their loot is a mix of gold and non-magical items.