Pour this serum into the river to make the water oily for 15 minutes. Using this item on the river will permanently consume one charge from your Armory supply upon expiration of the effect. Charges do not get consumed if the effect is replaced by a stronger vial before expiration. Vials can only be used if at least one charge remains in your Armory. Charges will only be used by successfully enchanting the river, and will not be consumed if the item is sold, dropped, or destroyed during a game. You can only cast a vial on the river if there's not a stronger vial already in effect.
Can only target the water in the river.
Oil's strength is in the middle. It can be replaced by Electric, Potion and Blood, but not by Chrome, Dry and Slime.
River vials accordingly from weakest to strongest: