From publisher blurb:
In this Christmas one-shot the players will be playing an elite hit squad of elves sent on a secret mission from Santa. The mission is clear, infiltrate Krampus’s evil workshop and put an end to his evil doing in time to save Christmas.
This is written as a stand-alone adventure, but it could easily be added into your campaign by having Santa request the help of the existing party or introduce the mission by whatever plot hook you decide.
This one-shot is balanced for level 6, but a level 5 party may survive if they are smart.