Before we launch an assault on Fenris Isle, we must determine who is behind the rot hide gnolls.  Our apothecaries believe their origin lies within the strange fluid that flows through their bodies.$B$BGo to Fenris Isle, east of the Decrepit Ferry, and collect rot hide ichor from the gnolls you find there.  Bring it to Apothecary Renferrel, stationed outside the Sepulcher.