Galbadia

Squall04 he knows that because it's part of Diablo's profile

Found at: Speak with Headmaster Cid before leaving for Timber and he'll give you a cursed Magical Lamp. Use the lamp in your inventory, and you'll get teleported into battle against Diablos. You must defeat Diablos before it will join your party. You should be warned that Diablos without a doubt is the smelliest GF in the game.

Note: Diablos has an aversion to bathing (water in general) therefore he does not work well with Leviathan.