Here is the full list of all 16 Masky achievements.
get Hellatin mask
get Traino mask
get Graven mask
get Cosmoid mask
get Laboratous mask
get Hospitalion mask
get Candycox mask
get Woodorn mask
get Wetto mask
get Catalis mask
Win 10 multiplayer battles / dances
Win 30 multiplayer battles / dances
Win 100 multiplayer battles / dances
Dance for a total of one hour
Dance for a total of five hours
Dance for a total of 24 hours