Dualcast

Doublecast, also known as X-Magic, Dualcast, or Double, is a recurring ability which allows a character to cast two spells in one turn.

Final Fantasy IV
Dualcast appears as a Augment Ability in the Nintendo DS version. It is obtained by speaking with the Mysidian Elder if the player gave three Augment abilities to Palom and Porom before they left the party, with each twin having at least one ability each. Dualcast is compatible with all forms of magic.

Final Fantasy IV: The After Years
Golbez and Fusoya can perform Double Black as a Band Ability, and can cast Double Firaga, Double Blizzaga, Double Thundaga, or Double Meteor.

The ability Dualcast' can be extracted from the Dark Crystal on the 15th floor of the Depths. The ability is acquired by defeating the optional boss Deathgaze, and can only be learned by Palom, Porom, or Leonora.

Final Fantasy V
Dualcast is the Level 4 ability of the Red Mage. Dualcast notably works with most types of magic, even Summon Magic. The only exception is Blue Magic. However, these magic types must still be equipped to be used with Dualcast. Because it is a form of Red Magic, Dualcast on its own gives access to a handful of basic White and Black magic spells without the character having any other magic types equipped.

Final Fantasy VI
Dualcast, also known as X-Magic, can be used if a character is equipped with the Soul of Thamasa Relic. The only drawback is that the character cannot summon the Esper he or she currently has equipped.

Final Fantasy VII
The W-Magic Materia allows a character to cast two spells in one turn. The somewhat similar Quadra-Magic Materia lets the linked Magic Materia be cast four times for the cost of one casting.

Crisis Core -Final Fantasy VII-
Dualcast is a Support Materia Zack Fair can either buy from the Network Shop Shade or find in a chest during Mission 9-1-4. When any Magic Materia is used while Dualcast is equipped, it is cast twice in succession.

Final Fantasy VIII
Double (ダブル, Daburu) and Triple (トリプル, Toripuru) are spells usable by the player, and by some enemies. The Double spell inflicts the status effect of the same name, while Triple inflicts the Triple status. When under Double or Triple status, a character may cast a spell two or three times at once, at the cost of expending more spells from their stock than normal. Cerberus casts both on the party when summoned. Some Guardian Forces have the abilities "Expend x2-1" or "Expend x3-1" that only removes one spell from the caster's stock when Double or Triple are used.

Double is a fairly common spell in the early stage of the game, but it can be drawn from very few normal enemies.

Triple is one of the rarest spells in the game and can only be drawn from bosses. It is one of the most powerful junctioning spells in the game, second only to Ultima.

Final Fantasy IX
Vivi's Trance ability is Double Black, letting him cast two Black Magic spells in one turn. Eiko's Trance is Double White, allowing her to cast two White Magic spells in one turn.

Final Fantasy X
Doublecast allows a character to cast two Black Magic spells in a row. It is located in Lulu's section of the Sphere Grid, but several locks must be passed first.

Final Fantasy XIII
Dualcasting appears as Paradigm consisting of two Ravagers.

Final Fantasy Tactics Advance
Doublecast is learned by Red Mages via the Madu. When used, it allows the unit to cast two spells from both of the A-Ability sets if possible. Doublecast works with White, Black, Summon, Spirit Magic, as well as certain Corner abilities. Doublecast can also be used to avoid some elemental, skillset, and Dmg2 laws because Doublecast is seen by the game as a non-aggressive, non-elemental, Red Magic ability. It is also one of few abilities in Final Fantasy Tactics Advance to cost 999 AP to master.

Final Fantasy Tactics A2: Grimoire of the Rift
Doublecast is again learned by the Red Mage for 990 AP via the Madu rapier. The game mechanics for it have changed, though; it is more sensitive to laws than its incarnation in Final Fantasy Tactics Advance. Though specific skillset laws have been abolished, the spells used in Doublecast will be sensitive to elemental laws.

Dissidia Final Fantasy
Terra's EX Mode bonus Chainspell allows her to use her magical attacks twice in succession.