Rydia/Gameplay

Final Fantasy IV
As a Summoner Rydia has high magic stats but low physical stats and can summon Eidolons.

Abilities
Rydia can use Black Magic and learns every spell, up to and including Meteor, but she learns them later than Palom due to her emphasis on Summon Magic. As a child, she can cast some basic White Magic. When she returns to the party as an adult, she has forgotten these spells.

In the 3D remake version, Rydia can learn more White Magic as a child, and learns her later Black Magic at different levels. Rydia joins the party at Level 7, while she joins at Level 1 in all other releases, and thus knows several spells already. When she is reverted to a child during her Lunar Trial in the Advance and Complete Collection releases, she can cast her White Magic while retaining all her Black Magic.

When Rydia rejoins the party as an adult in the Dwarven Castle after beating Golbez, she automatically has Fira, Blizzara, Thundara, along with Cura. At this point, she no longer has the White Magic command and cannot use her White Magic spells. So Cura can never be used outside of her trial in GBA and PSP versions, when she'll lose Summon Magic and temporarily regain White Magic.

In all releases, Rydia learns her Eidolons the same way.

Equipment
As a child, Rydia equips rods, staves, bows, daggers, and whips. As an adult, she loses the ability to equip staves. In the Game Boy Advance and PlayStation Portable versions, there is a loophole the player can use to equip the adult Rydia with a staff: when she transforms into a child in her Lunar Trial she regains her White Magic and the ability to equip staves, and will not remove any equipped staff she is given when the trial ends and she turns back into an adult. However, once the staff is removed it cannot be re-equipped without repeating the trial.

In the 3D remake, she cannot equip bows. Her armor is limited to universal equips and mage equips. In Final Fantasy IV Advance, equipping Rydia with the Mist Ring allows summoning the Mist Dragon to grant a Blink effect on the entire party.

Boss
Rydia appears as the Girl in the scripted battle with Cecil and Kain in Final Fantasy IV at Mist.

Final Fantasy IV -Interlude-
Rydia appears for the final battle against Rydia?. She knows all her Black Magic up to Blizzaga, has all her summons except for Goblin, Bomb, Cockatrice and Mindflayer, and is equipped with a Stardust Rod. She has 1100 HP and 330 MP. Her level and full equipment except her equipped weapon are unknown, as the player cannot enter the menu while she is in the party.

Stats
Rydia's MP and Intelligence are high, but her HP is among the lowest in the game. Compared to the other Black Mage of the game, Palom, Rydia's stats are inferior in all areas except for Speed and Spirit.

Abilities
Rydia retains her Black Magic, and her Summon ability, but she cannot summon anything as she loses all of her Eidolons at the start of her tale. With the exception of the Eidolons that are dropped by enemies, she cannot relearn them until The Gathering chapter, where the player must explore the world and defeat them. This is excluding Leviathan, Asura and Bahamut, who are fought and reacquired in the True Moon. The Chocobo Eidolon is also found in the Chocobo's Forest on an island west of Kaipo during The Gathering. Depending on the player's actions during the fights, it is possible Rydia may not relearn all her summons.