Tainted Keg is a quest item. It is made by poisoning a Keg of Shindigger Stout stolen from the dwarves of Dun Garok with a concoction created by Apothecary Lydon.
This item is provided for  Elixir of Agonyω τ ϖ.
Tainted Keg as a quest objective
This item is an objective of  Elixir of Agonyω τ ϖ.