An item needed for the Pre-Searing Ascalon quest The Poison Devourer. The Poisonous Stinger can be gained by killing the Plague Devourer in the devourer cave in Lakeside County. Like most Quest items, the Poisonous Stinger has no value if you try to sell it to merchants and cannot be salvaged.
Give this to brother Mhenlo to obtain the quest's reward.
Strangely enough, the Plague Devourer almost always drops 2 poisonous stingers, independent of the number of people in the party, but you only need 1. This is unlike most quest items, where the number of people in the party directly corresponds to the number of copies of the item dropped. A theory about this is that the Plague Devourer has 2 stingers, and therefore it drops 2 poisonous stingers.