Kersti

"As their caretaker, it's my duty to find all of them, or else I can't return to the Sticker Star!"

- Kersti

Kersti is a sticker fairy who appears in Paper Mario: Sticker Star. She is Mario's initial companion in the game. Kersti's name is an anagram of the word "sticker" but with the letter C removed. Kersti has the ability to "paperize" stickers by pressing, turning the stickers into objects that can be placed into designated locations. She also has the ability to create a tool used during any battle she is present in called the Battle Spinner; this is a slots-type minigame where Mario must match up two or more images in order to use more stickers per turn, and if Mario gets three of the same image, a special effect will occur.

In the end, she sacrifices herself when she lets Mario use her as a sticker during the final battle with Bowser, in order to overcome the power granted to him by the last Royal Sticker. However, after the battle, Mario brings her back to life by wishing on the Royal Stickers. Shortly after, she scolds Bowser for trying to steal the Sticker Comet again. She then jokes about considering to change her career, and Mario, Peach, and Bowser laugh.

Kersti is shown to be benevolent, but also has a feisty side to her. She has an aggressive dislike of Kamek.

She also slightly resembles a Pixl from Super Paper Mario.

Powers and Abilities
Kersti grants Mario the ability to use the Battle Spinner and Paperize. Like Goombario and Goombella before her, she can give area tattles (by pressing ), but not on enemies. Thus in certain scenarios when Mario is separated from Kersti, he can't use these abilities. In the final battle with Bowser, Kersti transforms herself into a sticker, and when used by Mario, creates a special battle spinner that always wins by landing on her image. Mario is slightly healed, and 5 sticker slots are created. Then for the rest of the battle, Mario can use 5 stickers in one turn, and the shielding power of Bowser's Royal Sticker is nullified.

Sticker Description
"Sacrifices herself to give Mario all her power, leaving everything to him."

Trivia

 * In both areas that Mario loses Kersti, the player is unable to save the game, nor return to the World Map. This is most likely so the player can't go to other places without Kersti.
 * With powerful stickers, it is possible to defeat Bowser entirely without ever using the Kersti sticker. She will remain in the album after the battle and can be tossed like any other sticker. However, it is unknown how she would be otherwise used in the game, as stickers are not saved after the credits.