December is the twelfth of twelve months in a year. In both the Kaelicious universe and the Hollideus universe, it is the month of the popular Christmas holiday and thus the favorite month of Christmas Elves and all supporters of the Idol of Christmas, because it is the time for producing toys and other presents to give out to all people of the world who have been nice throughout the year. However, many wish to destroy the holiday and its supporters for varying reasons, and thus December is often a month of conflict between those who support the holiday and those who despise it, namely the Idol of Halloween and his demon hordes from Hell, or the Shadow Cult.

For the different December-timelines of the two similar franchices, see December (Kaelicious) and December (Hollideus).