The Mist Dragon (ミストドラゴン, Misuto Doragon?), also called Dragon, is a summon that has only one relevant appearance in a main series installment, but has also appeared in spin-offs. Its trademark ability is the Radiant Breath, also known as Mist Breath.
Final Fantasy IV[]
The Mist Dragon's first appearance is small, but nonetheless vital. It guards the Mist Cave leading to Mist, and is summoned by Rydia's mother. When Cecil and Kain slay the Dragon, Rydia's mother dies as well. When they confront Rydia shortly after, it is this revelation, as well as the King's manipulations of them, that convinces them to rebel against the King's orders.
Later, when Golbez summons the Shadow Dragon to kill Cecil and his friends at the Dwarven Castle, Rydia, now matured to a young woman, intervenes, and summons the Mist Dragon, which uses Radiant Breath to kill the Shadow Dragon and leave Golbez open to the party's attacks. From that point on, Rydia can summon the Dragon freely in battle. It has a casting time of 3, costs 20 MP to summon, and does damage based on Rydia's current HP - the more HP she has, the more damage it does.
The Advance release adds in Rydia's "lunar trial" based on her summons. Her trial within the Lunar Ruins involves her reverting to child form and having to fight four of her summons, then fighting the Lunar Dragon, a powered up Mist Dragon. Killing it earns the Mist Ring which adds a single Blink image to the party after preforming its attack.
In the Nintendo DS release, the Mist Dragon's design is that of a Japanese dragon, rather than the appearance of a European dragon as in the original releases. Its non-elemental attack was changed to the Holy-elemental and its Mist Breath was renamed to Radiant Breath. In addition, its summoning cost was increased to 35 MP.
Final Fantasy IV -Interlude-[]
Mist Dragon returns as a Summon spell for Rydia in the sequel of Final Fantasy IV. It deals moderate non-elemental damage to all enemy at the cost of 20 MP. When the real Rydia appears, she summons the Mist Dragon to knock some sense into Bahamut who dismisses himself from battle after being hit by Mist Dragon's Radiant Breath.
Final Fantasy IV: The After Years[]
During Kain's Tale, the Mist Dragon intervenes when Ceodore and the Hooded Man are escaping from Baron soldiers in the Mist Cave. If the player inspects the gravestone of Rydia's mother in the village of Mist, the Hooded Man will express his sincerest gratitude for saving their lives.
If the player visits Mist during the Gathering Tale, the party discovers the Mist Dragon has protected the village from the meteors. Rydia calls out to her mother, who tells her she cannot leave the village until the other Eidolons have been freed. When the task is completed and Rydia returns, she asks the villagers why the Mist Dragon was not mind-controlled, unlike the other Eidolons. They tell her it was the work of the children and the villagers, who only have a fraction of Rydia's power, and pooled it together to protect her mother's dragon. Rydia's mother tells her she will always be with her and the villagers. The Mist Dragon then returns to Rydia.
The Mist Dragon costs 35 MP to summon and deals non-elemental damage to all enemies. Its spell power is 120.