Christmas Advent Calendar is a Treasure Hunter promotion that ran from 1 December 2018 to 25 December 2018. During this promotion, different prizes were available to be won from Treasure Hunter each day. Players could also claim one free item each day from the Advent Calendar. Players could retrieve any items they may have missed during December up until 7 January 2019.
The Advent Calendar could be accessed in the Community tab (default keybind is F5).
When claiming a prize, the message: Your advent present has been added to your backpack. was given.
Christmas Advent Calendar