The Santa's Rampage DLC content was merged into the main game on December 8, 2015 along with the update to v1.04, and like VCD:SW, is now free with the base game. The standalone version is still available to purchase and play separately.
Viscera Cleanup Detail: House of Horror was the third expansion created for the game, and the second holiday-themed level. It introduced a fairly large map, all new custom content and level mechanics, an original soundtrack, 10 achievements, collectible items, and several "easter eggs" related to the Halloween theme. It was released October 29, 2015 on Steam along with an update to v1.01. (The respective Runestorm blog update can be found here.) It is the first paid DLC in the collection, and requires the base game to play.