Inundated by Evil  

These repeatable kill tasks are given by Commisioner Dogweed in Rivervale after you complete the Once Upon a Plague quest for him.

He will ask you to kill 10 of a random type of monster in Rivervale. Previously this quest was only for corrupted bandits and brigands, now it offers an assortment of kill tasks (see related npcs for details).

You do not need to return to him after the quest is over, you will automatically receive your reward. You can return to him however to open up the Fighting the Infestation quest.