Once Squall, Zell, and Selphie are promoted to the rank of SeeDs, early on in the game, they will be sent on a mission to the town of Timber to help the local resistance group the Timber Owls. After a mission briefing from Cid the party is sent out into the world where they would normally head to Balamb to take the train to Timber. Before leaving Balamb Garden if the player talks to Cid again he will give them an item called the Magic Lamp. If used on the world map the lamp will automatically thrust the player into a battle with Diablos, the dark magic using GF.
It is best to challenge Diablos to a fight as soon as possible. The longer you wait the more Diablos scales to your level, but he will actually stay a bit stronger than your team. Diablos can be a difficult fight even in the beginning of the game. A common gameplay tactic is letting Diablos use his attacks which deal damage to your health based on a set percentage on your characters until they get their limit breaks. Squall and Zell’s limit breaks, while weak, lets the player hit multiple times, leading the damage to add up quickly. Selphie’s limit break can be used to “Do-Over” until you get the Full Cure magic.
It is possible to Draw-Cast Diablos’ Gravija magic right back at him, but the chances of the draw working successfully are very slim.