Frost Moon

The  is an event added in 1.2.2 that can only be triggered in Hardmode through the use of a Naughty Present. It is the Christmas counterpart of the original Pumpkin Moon with increased difficulty, making it the most challenging event introduced thus far. It has 15 standard waves as well as 5 extra bonus waves.

During this event, the moon changes color to look like the face of a snowman.

Aside from the unique rewards you can get from the monsters in Frost Moon, this is also a very good source of Presents.