The Etherian Holiday Extravaganza Add-on for Dungeon Defenders has 5 achievements.
You survived the onslaught of the Holiday Guardians!
You survived the onslaught of the Holiday Guardians... on Nightmare!
Delivered all the presents, and saved Santa Tavernkeep from the vile clutches of Mega-Snowman in the 'Etherian Holiday Extravaganza Challenge Mission'!
You delivered Santa's goodies... and then took on the big man himself!
You delivered Santa's goodies... and then took on the big man himself... on Nightmare!