Spirit

A Summon Spirit is an elemental being that can be called forth by a Summoner in the Tales series by Namco. Summoning is generally the strongest ability that players can use besides the Hi-Ougis (Secret Techs). So far, Summon Spirits may be summoned in Tales of Phantasia, Tales of Eternia (in which they go by the name Craymels), and Tales of Symphonia. They appeared in Tales of Legendia, but were never summonable.

Summon Spirits in Symphonia and Phantasia
Efreet is a ghost-like creature in Tales of Phantasia. When summoned, he fires many fireballs at enemies at random. In stark contrast, Efreet appears in Tales of Symphonia in a much closer concept to his namesake. He is a large, powerful looking demon-like entity who attacks enemies with a single powerful explosion. In both games, he is located in a desert cavern close to an oasis town. He is named after fiery Ifrits of Islam, who are very powerful Djinns (Genies).
 * Efreet, the Ruler of Hellfire, the Spirit of Fire:

Undine is depicted as a swordswoman in both Tales of Phantasia and Tales of Symphonia. In Symphonia, she is more amphibian-like, with completely blue skin and "clothes" that seem fused to her skin. When summoned, she uses four geysers (similar to a spell called "Spread") to damage enemies. Undine is the first spirit to be found and the only one other than Volt and Origin that has a large role in the story. She is found on a small island known as "Thoda," which is famous for its geyser. In Phantasia, she is a tall woman wearing typical blue flaps and cloth over her body with a sword. She flashes across the screen and hits enemies with an attack. In this game, Undine is found on an island with a sunken temple-cave, very similar to Symphonia.
 * Undine, the Maiden of the Mist, the Spirit of Water:

The Slyph are the first spirits to be summoned in Tales of Phantasia. They seem to be numerous, appearing as regular enemies within their mountainous region. Physically, they bear similarities to sprites. When summoned, they attack a single enemy with a weak attack. In Symphonia, there seem to be only three Sylph, and they are very powerful and work together to fight. Sephie, the apparent leader, carries an oversized sword, while Yutis uses a bow, and Fairess defends with an oversized shield. Sephie is the main physical attacker while Yutis provides support at a long range. Fairess heals the other two and attacks the party with wind spells. When summoned, they attack a single enemy in tandem for huge damage compared to the other attacks. In Symphonia, the Sylph are sealed in a large Temple that appears to be built in Meso-American architecture.
 * The Sylph: Sephie, Yutis, and Fairess, the Heavenly Messengers, the Spirits of Wind:

In Phantasia, Luna and Aska are separate beings. Luna is the Spirit of the Moon and Aska is the Spirit of Light. Neither of them fights the party, instead providing their services without resistance. Luna is found atop a twelve-story tower, while Aska is found trapped in a sunken city known as Thor. Luna attacks by calling many pillars of light upon the enemy; Aska attacks by flying into battle with other eagles, who damage all on-screen enemies with light. In Symphonia, they are treated as a single Summon Spirit, and the player must fight both of them simultaneously. Curiously, only Luna appears to attack enemies when they are summoned, but Aska and Luna appear separately when all the spirits are summoned at the end of the game. Luna and Aska are found on top of a tall tower, known as the Tower of Mana, which is located north of Luin.
 * Luna and Aska, the Light of the Heavens, the Spirits of Light:

Celsius is not present in Phantasia. In Symphonia, she is found on the frozen continent near the city of Flanoir. She appears to be a pale-skinned woman with short-cropped dark hair. She is clothed in a dark dress which is cut down one side to allow Celsius maximum mobility. When she fights the party, she uses her fists and her feet in martial arts-type attacks.
 * Celsius, the Disciple of Everlasting Ice, the Spirit of Ice:

In both Symphonia and Phantasia, Volt has a relatively similar appearance: that of a ball of energy with eyes. In both games, he does not communicate in the human language. In Symphonia, his speech is represented by ellipses, while in DeJap's translation of Phantasia, he appears to speak in binary. Also, Volt dislikes humans in Symphonia, but seems to be more pacified in Phantasia. Symphonia's Volt attacks with many lightning strikes in a large area, while Phantasia's Volt hits enemies with a massive blast of electricity. Volt can be found in Temple of Lightning, located on a northern island, in Symphonia, while he is found in a cavern (located south of Miguel), named in his honour, in Phantasia.
 * Volt, the Hammer of Godly Thunder, the Spirit of Lightning:

Unlike the other characters, Gnome has vastly differing appearances in Symphonia and Phantasia. In Phanatasia, Gnome stays in a cavern known as the Cavern of the Spirits. He looks similar to five rockets stuck in the ground. When he attacks, Gnome fires these rockets out of the ground, directing them to land upon the party. This makes it very difficult to attack him. (When summoned by the party, he does the same attack.) However, these attacks do not do much damage, either. This fact, coupled with the difficulty in hitting him, can draw out the battle's length. Symphonia's Gnome has him as a large mole-like creature, which Colette remarks as being "cute." Gnome carries a shovel and has a red "ribbon" on his head in this game. He attacks in a more typical Earth-element fashion, slamming the ground and casting Earth spells. Although his large size allows him to slam the party members to the ground, it also makes him a large and slow target for their attacks. Once beaten, Gnome remarks "Geez, you guys fight dirty with this four on one stuff." It is likely that, after being ganged up on, he split himself into multiple creatures to even the score in the future.
 * Gnome, the Servant of Mother Earth, the Spirit of Earth:

Shadow is one of the more enigmatic Summon Spirits. In Symphonia, he appears as a vaguely humanoid shape made of a dark substance (presumably shadow itself). He is found south of the Fooji Mountains. He does not use a physical weapon in battle, instead relying on his long arms to inflict damage. Shadow also uses dark magic. He is also able to dissolve into shadows and thereby warp around the arena at will. His speech is fairly basic, and he does not use full sentences when speaking (some examples would be "Mithos and I... Pact..." and "Fight...").
 * Shadow, the Envoy from the Dark Abyss, the Spirit of Darkness:

Origin is regarded as the supreme Summon Spirit, the most powerful and the undeniable king. In Symphonia, he is a muscular man with four hands (two of which hold swords and two hold staves), a protective shield of whirling spikes around his midsection, dark legs, and wild, light-coloured hair. In Phantasia, he has changed his appearance to a small fairy-being guarded by a Seraphim. Nevertheless, he is still quite powerful, being almost impervious to damage from physical weapons and impossible to harm from various elements. In Symphonia, it was Origin who created the Eternal Sword for Mithos Yggdrasill. He later grants Lloyd Irving, the game's protagonist, the ability to wield it. He also infuses its power into the two blades given to Lloyd by Kratos Aurion and Dirk, the Flamberge and Vorpal Sword. In Phantasia, it is Origin who brings the Flamberge and the Vorpal Sword together to (once again) create the Eternal Sword. The citizens of Aselia in Tales of Phantasia regard him as the Lost King of the Dwarves, which means that Origin has the ability to forge powerful objects. This may be a reference to Lloyd Irving, who was was raised by a Dwarf.
 * Origin, the King of the Summon Spirits (Symphonia), the Lost King of the Dwarves (Phantasia):

In both games, Maxwell is linked to the elements of Earth, Wind, Fire, and Water (more specifically, Gnome, Undine, Efreet, and Slyph). In both games, he appears to be an old man sitting on a flying disk. Tales of Phantasia regards him as the head of the Lower House of Summon Spirit, the Earthly Elements. He is located in the underground Morlia Gallery. In Symphonia, he is an optional boss and Summon Spirit. It is his duty to keep the city of Exire, home to the ostracized half-elves, floating above the world. It is ironic that he relocates himself to the deep Morlia Gallery, the abandoned home of the Dwarves, one thousand years later. In Phantasia, summoning him causes him to appear in the form of seven orbs which bounce around the screen and hit the enemy. In Tales of Symphonia, Maxwell attacks the enemies with the deadly Meteor Storm, arguably the most powerful attack in the game.
 * Maxwell, the Master of Matter (Phantasia), the Spirit of Molecules (Symphonia), the Spirit of Birth:

Summon Spirits in other Tales games

 * Chameleon, a creature from Daemonium that attacks with its tongue. It can kill a foe instantly (Phantasia only)
 * Gremlin Lair, who summons creatures from Daemonium to attack its foes (Phantasia only)
 * Pluto, who summons a Lich-like creature (Phantasia only)
 * Rem, who summons an angel-like creature (Eternia, also appears in Legendia)
 * Destiny, summons the characters from Tales of Destiny (Eternia only)