"Undead Santa seeks out those who have been naughty by breaking into your base. Discovered under the Special Snowflake in the 2015 Holiday Event."
The Undead Santa is a Collectible-tierd re-skin of the Undead Guardian. This came out of the Super Snowflake Artifact in 2015. It appears to share the same appearance as the Undead Guardian except for the hat and the beard. It has exactly the same effects and abilities as a regular Undead Guardian, with the exception of it having a "ho ho ho" sound effect.