From Final Fantasy Wiki

Yuna, performing a summoning ritual in Final Fantasy X

Summon, also known as Call, Conjure, or Summoning, is a recurring ability in Final Fantasy. It lets the user call summoned monsters into battle to help out. Whenever the player Summons, flaming green orbs, usually three in number, will float out or encircle the player character.

Appearances

Final Fantasy III

Summon can be used by the Evoker, Sage, and Summoner jobs, with different effects. Evokers and Sages will randomly summon an "offensive" or "defensive" attack from a chosen summoned monster. Offensive attacks may deal damage or inflict status effects, while defensive attacks usually buff up and/or heal the party. The Summoner can use the Summon at full power.

Final Fantasy IV

Known as Call in the SNES version, Rydia has the ability to Summon Eidolons to do massive damage.

Final Fantasy V

Summon command lets the Summoner class call forth a regular summon beast to deal massive damage to foes.

The Call command, known as Conjure in the RPGe version, causes a random summon for 0 MP.

Final Fantasy VI

Summoning Espers is accessible as long as a character is equipped with Magicite, by selecting the Magic command and pressing the Control Pad upwards while at the top of the list. Most summons have unblockable attacks that cannot be reflected, but can only be summoned once per battle. In addition, equipping the Celestriad Relic will reduce the MP of summoning costs to 1.

Final Fantasy VII

Summon command is accessible as long as a character is equipped with Summon Materia. The times the summon can be called is dependent upon the materia's level, although using the Master Summon Materia allows a character to summon anything, any time, any given number of times in a single battle, as long as they have the appropriate MP.

When Summoning, characters are surrounded by a flash of light. Several spheres of color with strange symbols float up while the character stretches out their arms. They disappear just before the Summon performs its attack.

Final Fantasy VIII

GF command appears when a character had junctioned a Guardian Force with the command. However, the GF is not summoned right away. A second ATB bar appears over the summoner's, and when it depletes the summon is used. The GF's own HP replaces the summoner's for the duration of this, and if the GF's HP is depleted, the summon is canceled, and the GF cannot be summoned until it is healed.

Final Fantasy IX

Eiko and Garnet summon Alexander

The Summon command is used for both Garnet and Eiko, although each have access to different summons. In Trance, Garnet's summon command will be named Eidolon. In this mode, an Eidolon called by Garnet will randomly appear to attack even after it has been dismissed after its initial summoning.

The Mimic can also call forth a minion through the Call command. A Mimic will call a Magic Vice to assist them in battle. If the Magic Vice is defeated, only then will the Mimic will use the same command again.

Final Fantasy X

Only Yuna has access to the Summon command. When she summons an aeon, the rest of the party leaves the area. It is the first Final Fantasy in which the summoned creatures can be controlled.

Final Fantasy XI

Summoners and characters with Summoner as their secondary job have access to the Avatar and blood pacts that they have earned. In this case, the summoned creatures are each considered their own spell and are unable to be called in the event the summoner is silenced.

Final Fantasy XII

The Summon command, found under the option Mist, enables a character to summon the Esper acquired in the License Board. In the International version of the game, the Espers can be controlled by the player.

Final Fantasy Tactics

Summon is a command ability, learned from the Summoner job class. In order to use it, the unit must have purchased at least one summon.

Final Fantasy Tactics Advance

Summon is a command ability, learned by the Summoner job class. Summons are learned via staves.

Final Fantasy Tactics A2: Grimoire of the Rift

Summoning is a command ability, again learned by the Summoner job, which can only be accessed by Vieras. Staves teach summon magic.

Gallery

Bahamut being summoned in Final Fantasy III	Rydia summoning in Final Fantasy IV (DS)	Bahamut being summoned in Final Fantasy VI	A Summon in Crisis Core
Cloud summoning Knights of the Round in Final Fantasy VII	Squall summoning a GF in Final Fantasy VIII