No Man is a Fortress

 is a limited time side questline released on December 19, 2015, along with the Winter 2015 Event's Act 2. To start the quest, the player had to complete Once In Royal Quimby's City Pt. 4, The Animal Within Pt. 2 and Holiday Mystery Meat Pt. 1.

Quests
* see the detailed list of the tasks to upgrade the "Fortress of Lonelitude" here