Land of Summons
Hydra and Dragon becoming summons
Esperville
Ultimate Destructive Magic Meteor and Holy
Guardian Forces causing amnesia and Griever being drawn out of imagination
Ramuh, Atomos, Bahamut, Odin, Alexander, Madeen
High Summon
Eidolons challenging L'Cie

Final Fantasy Summons and their Summoner always are a major element.

There are enough classes in the spotlight.