Bahamut is the last Eidolon summoned by Rydia? in Final Fantasy IV -Interlude-. It is fought in the Tower of Babil after the first four Eidolons are defeated. Rydia? tries to finish off the party with Bahamut, but the real Rydia appears and summon the Mist Dragon to knock some sense into Bahamut who dismisses himself from battle which leads up to the the final boss.