Costume Sets are a type of bonus effect similar to Cookie Bonds that are activated by collecting certain Costumes. Alongside these sets are short stories explaining the context behind the Costumes, giving backstory to the different sets. The buffs provided through these Costume Sets automatically apply to all of a player's Cookies with more bonuses given for each Costume in a set that the player owns, and the individual bonuses from each level of a Set stack and add up.
Unlike Cookie Bonds, the bonuses provided do not depend on the Cookie's promotion level nor whether the player even owns the Cookie for whom a Costume is made. Simply owning the appropriate Costume grants a passive bonus.
Each Costume Set grants its own buffs based on the number of Costumes in it owned, with all buffs from different Costume Sets stacking with each other. Certain Legendary Costume Sets also grant a limited-time Title if both Costumes are collected within a given period of time.
List of Costume Sets