While magic is just a battle command or an ability, the link between Rydia and her summons is more profound. Unlike spells, summons are living beings and one just does not learn a summon as he does with a spell. An Eidolon isn’t a mere battle tool, but a creature who develops a special connection to the summoner they are serving and, vice-versa, a summoner has a special connection with their Eidolons.
While the ability of summoning is a birth right, acquiring a summon requires a bit of work. Considering what Rydia must do during the game to gain a new summon, it may be supposed that a law of summons takes place1. The code says “test the caller before you answer the call”, which means a summoner must defeat the summon, before being able to be granted their service. It must be noted that a summoner doesn’t control a summon by sheer force, rather summons help a summoner because they have earned their respect by proving their worth. Like black magic, summon magic requires caution. Calling forth a summon without being able to actually control them may have a boomerang effect on the summoner, who unleashed an uncontrollable beast. This is the reason why a summoner must be certain to know his Eidolons and his own strength beforehand.
Asura. Aside from small cameos in some spin-offs, Asura is a Final Fantasy IV-exclusive character.
Asura reigns over the Feymarch, where all Eidolons live, together with her husband Leviathan. Asura is a support summon and can cast three different healing spells (for example Curaga, Life and Protect in the Advance release), depending on the face shown when summoned. The fight against Asura is optional, although it is compulsory to defeat Asura in order to be able to fight against Leviathan.
When Rydia returns to the Feymarch, Asura is pleased to see her again and willing to become one of her Eidolons (not without the compulsory fight, though):
Asura: Rydia…It is good to see you again, and well.
Rydia: Please, Your Majesty…We have need of your strength!
Asura: Then I shall lend it to you. But you know I must first test your own. It is the Code, and the Code must be observed. Have you the courage and strength to face me? So be it!
[After battle]
Asura: Sweet Rydia…These are good companions you have found, both strong and true. Allow me, too, to lend my strength to your cause. Summon me whenever you have need.
- The law of summons concept isn’t developed a lot Final Fantasy IV, but it is more structured in some of the later Final Fantasy. One example is Yuna of Final Fantasy X. Before being able to acquire a new summon, a summoner and their guardians must solve the puzzles found in every Cloister of Trials. Once the puzzles are solved the summoner alone can proceed to the Chamber of the Fayth. There the summoner has to pray the Fayth and, if their prayer is heard, the Fayth will join them as a Aeons (which basically is an equivalent for Eidolon). [↩]