Costumes are key items that allow the player to change their appearance. When starting a new game, the player will wear the casual Monster Keeper outfit, but as the player explores the Sanctuary and progresses in the game, they will be able to obtain more costumes from chests or by reaching certain achievements. The player can change their costume by talking to the Stylist in the Keepers' Stronghold. There are nine types of costumes for both gender expressions, and each comes with six variations. In total, there are 108 costumes altogether.
Costumes are carried over when playing New Game+. Reward Box lvl 1 replaces chest contents or rewards that give the player a costume they have obtained.