Costumes

Outfits are sets of clothes for the Beheaded. They are unlocked by finding their blueprints and buying them at the Collector with cells, much like the other upgrades.

Once at least one new outfit is unlocked at the Collector, the player can change clothes by entering the Tailor's shop at the start of Prisoners' Quarters.

Outfits change the colors and shape of the player model. Some specific outfit elements, like the Concierge outfits' shoulder plate, change color depending on the player's gear. Many outfits reference enemies (e.g. Ninja Outfit), bosses (e.g. Temporal Outfit), fictional characters unrelated to Dead Cells (e.g. Piccolo from Dragon Ball), or the game developers (Carduus Outfit).

Obtaining outfits
Outfits drop from enemies and bosses, or are found in secret areas around the island.

For outfits dropped by enemies, the Hunter's Grenade can be used. Unlike most blueprints, some outfits will only drop from enemies with a certain amount of Boss Stem Cells active, even if those enemies can be found at lower difficulties.

Bosses drop up to 5 outfits, one on each difficulty level from 0 to 4 BSCs. The outfit of the lowest difficulty will always be found first; the 0 BSC outfit will drop before any others even if the player is on Nightmare difficulty.

Trivia

 * Outfits were added with the v1.2 release of the game, also known as the Rise of the Giant DLC.
 * While all costumes are in the base game, some of them cannot be legitimately obtained without installing the Rise of the Giant DLC or the Bad Seed DLC.
 * The Flying Alcoholic Outfit was previously called the Christmas Outfit.
 * Outfits that drop from Mama Tick and The Time Keeper give the beheaded a female body.