The bottle can be used with the "Red mist" that appears after an Armoured zombie is killed to create a bottle of mist. To pass the doors in the armoured zombie dungeon the bottle must be filled with a certain amount of the "red mist" obtained from killing the zombies. It is currently unknown but the red mist is suspected to be the blood of the Armoured zombies, despite that all other zombies in the game do not leave behind this mist.