I was just done collecting some Shards, putting them in my Vault, when I went to check my gift chests.
To my utter surprise, inside were two items I didn’t remember getting from the Calendar: an Ice Tomb Key (I didn’t buy any) and a Christmas Tree Cupcake (reskinned Grapes).
Was this some additional, hidden reward for today?
You can also notice the Advent Token and the 3 Santa’s Bags, which were login rewards from yesterday and a few days ago.
Link to the Login Calendars of 2018. As you can see, no other rewards are listed for the 13th.