Location
	Speak with Cid, before you embark on your quest to Timber. He will then hand you a Magic Lamp. When you feel you are ready, activate the lamp, and you will be taken into a fight with Diablos. Beat him, and you will gain him as a GF.

Diablos
	Elemental: None
	Attack: Dark Messenger
	Level	HP	Atk. Power
	9	730	9% DMG
	10	784	10% DMG
	20	1326	20% DMG
	30	1876	30% DMG
	40	2434	40% DMG
	50	3000	50% DMG
	60	3574	60% DMG
	70	4156	70% DMG
	80	4746	80% DMG
	90	5344	90% DMG
	100	5950	100% DMG

Ability	AP	Opens		Ability	AP	Opens
HP-J	50	HP+20%		HP+80%	240	None
MAG-J	Learned	NONE		MAG+20%	60	MAG+40%
Hit-J	120	None		MAG+40%	120	None
Abilityx3	Learned	None		Mug	200	None
Magic	Learned	None		Enc-Half	30	Enc-None
GF	Learned	None		Enc-None	100	None
Draw	Learned	None		GFHP+10%	40	GFHP+20%
Item	Learned	None		GFHP+20%	70	GFHP+30%
Dark	100	None		GFHP+30%	140	None
HP+20%	60	HP+40%		Time MAG-RF	30	None
HP+40%	120	HP+80%		ST MAG-RF	30	None

At first, Diablos seems pretty weak in the attack department. Sometimes doing less than 100 Pt's in damage. But once he gets some levels under his belt, he becomes one of the most lethal GF's in the game. That said, there are more enemies than not, that are immune to his attack.
Diablos comes complete with a plethora of useful abilities. Mug is perhaps the best of the best. You can easily steal needed items from your enemies (And if you keep Squall in HP critical for limit breaks, it is a good way to know it is him). Enc- Half and Enc-None are very useful, when trying to get through area's with time limits, or if you just do not feel like battling. Hit-J gives your party a boost in hitting ability, and the HP+20/40/80% are great boosters, especially if you get him early in the game.