Vermintide 2's latest Back to Ubersreik DLC brought in five new weapons to toy around with, three remastered classic maps to explore, and perhaps most impressively of all, a lengthy treasure hunt that led to a secret new game mode! I won't spoil the surprise if you're up for hunting down all of the secrets yourself, but what I will say is that Fatshark has now also added a second treasure hunt as a part of the festive Mondstille update!
You'll find all of the details in-game as a part of an achievement, but long story short, you'll need to scour four specific maps in order to find hidden bonfires that unlock the very first (and very icy) animated portrait. These maps are: Hunger in the Dark, Fort Brachsenbrucke, War Camp and Skittergate. The Skittergate and War Camp ones are fairly easy to find if you look for strange new additions, but if you're going in blind for the Hunger in the Dark and Fort Brachsenbrucke ones, do make sure to be thorough with your search as they are rather deviously hidden!
Besides the new treasure hunt, the Mondstille update has also added some much-needed balance changes to the DLC weapons. Dual Hammers have had their damage and animations improved, the Mace & Sword combo has had its range increased and its damage decreased, while Sienna's Crowbill has finally gotten a nerf to its damage so it'll no longer one-shot Stormvermin with light attacks. You can find all of the details, as well as 'developer commentary', over at Steam.
The final thing worth mentioning is that this update has also brought in a double XP weekend. So if you have any characters you haven't fully leveled just yet, make sure to take advantage of the new event before it goes away on Dec 25th at 19:00 CET. Have fun!