The Elementals are the embodiments of the four main elements that make up the world: ice, fire, candy and slime. They have existed since the beginning of life, living, dying and reincarnating for eons and millennia. The current Elementals include Patience St. Pim (an Ice Elemental from the past that froze herself to survive to the Mushroom War), Flame Princess, Princess Bubblegum and Slime Princess.
The Elementals are introduced in the episode "Evergreen". Back then, the four Elementals were Urgence Evergreen (Ice), Chatsberry (Candy), Balthus (Fire) and Slimy D (Slime).One day, they met to talk about an incoming green meteor set to hit Earth filled with evil magic. The other Elementals do not worry about it, stating that although they will die, the elements they are representing will still exist, but Evergreen insists that they must act by creating a magical crown that will grant the wearer's innermost wish. Evergreen states that he must wear the crown, because his deepest wish is to destroy the comet. The other Elementals are against this, as they believe that the crown will corrupt Evergreen. Evergreen then fights the other elementals and ends up freezing them. After achieving to create the crown, Evergreen was unable to use it because he was crushed by debris from the attack of Magwood. Therefore, he instruct his apprentice Gunther to use it instead, but because Gunther's only wish was to be like Evergreen, the magic morphed him into a smaller version of him. When the comet finally hit, it resulted in the death of Evergreen.
In "Elemental" an Ice Elemental named Patience St. Pim is discovered by Finn, Jake and Ice King, frozen in a boat below Ice King's castle. She frozes Finn and Jake and instructs Ice King to reunite Flame Princess, Princess Bubblegum and Slime Princess. Then, she revealed to them that they are the current incarnations of the other three Elementals. She also tells the story of how she used to be the Ice Elemental in antiquity until she and the other Elementals began to have visions of the future about a cataclysm that would involve the end of the world as they were known. Patience suggested that she could save their lives if only frozen and waited for the transision happen but the other Elementals refuses, so she frozes alone and the others died. Finally reunited with the other Elementals, Patience shows them their potential powers, and attempts to make them unite, but the three Princesses show no interest in that. The Princesses then use their newly discovered powers to make her loose her balance and she crashes into her boat. While she was on the ground, the Princesses free Finn and Jake and escape; Slime Princess also shoots slime at Patience, sticking her to the wall. With Finn, Jake, and the Princesses gone, Patience, makes Ice King scrape all the slime off her and she tells him that she will make people know of her presence in Ooo.
Each Elemental have the ability to generate and manipulate their respective element. However, these powers are limited if they are in a non-magical world.