The Craymels are the spirits of the elements in the game Tales of Eternia for the PlayStation (Tales of Destiny II in North America) Each element (Fire, Earth, Water, and Ice for example) has a different physical representation that can be summoned for various purposes. (Efreet, Gnome, Undine, and Celsius, respectively.) Among the main natural elements, time is represented and various elements are represented. They are also the source of the game's magic system, called "Craymel Artes", and can teach both damage inflicting spells as well as innate supportive effects.
In order for a human to use Craymel Artes, the Craymel spirit must be encased in a special cage designed for such spirits. Gameplay-wise, Meredy and Keele used Craymel Cages, since they were the magic users in the game. When two cages have at least one Craymel, Meredy and Keele were able to fringe the two, resulting in a newly learned spell. Stronger spells are learned this way, and are usually sacrificed from previously used spells, depending on how you decide to align the Craymels in each cage. Aside from the arsenal of spells the Craymels grant Keele and Meredy, the Craymels themselves are also able to be summoned in battle under specific status conditions. In order for the ten usable craymels to go into a Craymel Cage, you must defeat them in a boss battle in their respected domain (the exception is Sekundes, who gives you his help for free - battling him is optional).
Undine, Sylph, and Efreet are the Greater Craymels of Inferia, the world where Reid, Farah, and Keele come from. When these three Craymels fuse together, they create the Governing Craymel of Light known as Rem.
Gnome, Celsius, and Volt are the Greater Craymels of Celestia, the world where Meredy, Chat, and Max come from. When these three Craymels fuse together, they create the Governing Craymel of Darkness known as Shadow.
Maxwell and Sekundes act as a Supreme Craymel on their own, without the use of other Craymels fusing together in order to maintain existence. They are also secret Craymels in the game, and are unlocked through side quests.
Though Keele and Meredy seem to be the only full-potential Craymel Mages in the game, a couple characters in the game have been known to use Craymel Artes for minor purposes. An example is one character helping Reid, Farah and Meredy down a river when he cast a Craymel Arte to calm the water.
The Greater Craymels are also characters that have made more than one appearance in the Tales series. Though not present in all installments, whenever there was a summon-like feature, these characters would make a recurring role.
Though just speculation, the word Craymel could have been derived from the word "crayon", since all of the Craymels' elemental symbols in the skill menu are distinguished by differentiating colors.
This list mostly goes by chronological order of obtaining the Greater Craymels. The exception is Shadow, who can be enlisted either before (CD2) or after (CD3) Rem.