Kill 8 Fen Creepers, then return to Rethiel the Greenwarden in the Wetlands.
I do not know why, but a festering grows within the Wetlands. Fen Creepers have risen. They are diseased, fevered blisters on the land, and for the fever to break they must be dispatched and allowed to settle back into the marshes.
The Fen Creepers shamble amidst the waterways of the Wetlands.