Vile fish are used in the Dungeoneering skill and are found only within Daemonheim. It is used in a puzzle room in which a player has to fish raw vile fish and cook it on a fire. Then, the player must throw the fish onto tiles in the centre of the room to navigate the ferret onto the pressure pad, while avoiding the holes. Vile fish cannot be eaten and are only used to solve this puzzle room.
When thrown on the tile, it becomes an NPC with the name "Bait" and the examine text "This attracts ferrets."