Due to the Red King's plot........The Blue King is pushed to the corner and calls for help.........and one of them is the maker of all of the Barrels........
its the "Barrel Master
"....he is similar to the Knight though he is carrying a barrel in his back...when he dies he drop the barrel that contains one of every spirit there is...Fire Spirit, Ice Spirit, Shock Spirit and Gust Spirit.....about 4-5 elixirs i think.
It seems that the Spirits is in good terms with the Barrel Master...they even help him to make those barrels.
(Barrel Master and Spirit Barrel has been combined from here https://communityroyale.com/index.php?p=/discussion/8706/d1nonlines-upcoming-cards-spoiler-more