A Christmas spirit jar is an item received from Kris during the 2011 and 2016 Christmas events. In order to create the Christmas banquet, Kris asks players to fill up the jar with Christmas spirit by using the jar on NPCs or other players three times. When used on a player or NPC, you will say "Merry Christmas (name)!" When the jar is full and used on another player, the extra spirit just escapes into the air.
After the jar is full, it can be used on Kris to help prepare the banquet.
Kris can give out multiple jars, letting players continue to use the Christmas spirit jar to collect Christmas spirit. The jar is removed from the inventory upon leaving the area.