Inside the Magical Lamp that you received from Cid is a horrible beast that you have conveniently woken from his nap (Yay...). I highly suggest saving your game before even thinking about challenging Diablos!
(By using the lamp from your items list on the menu you are automatically thrust into battle, and you cannot escape)
HP:1600-80,8000
AP: 20
Weak vs. wind
Flying monster
challenge Diablos because it will be just as hard as if you were in the beginning of the game not only because Diablos will retaliate and level up also but because do you honestly know how long it takes to gain
200 AP to get his Mug ability? A long time, to long. Also it takes forever to get Diablos's stats up to date with you other GF's. It took me 3 days to get his levels where I wanted them. Anyway I just want to make
that clear that is it best to take him on as early in the game as possible.
There are two ways that you can go about this battle. Diablos carries the spell Demi which is very powerful, probably more powerful than your GF's. You can use this spell against Diablos, although it will not be as powerful as when Diablos cast Demi onto your party but it is probably the best way to go. The Gravija attack will lower your
party's stats so that they are able to use there limit breaks. This is an especially good way to go if you have Selphie in your party because she
allows you to use her Full-Cure spells on your entire party bringing there HP levels all the way up.
I suggest putting Selphie into your party for this fight. He stats will most likely be lower than any other of your chars but she is very useful for this battle.
I chose to incorporate both options for defeating Diablos into my technique. I started out by having the entire party draw and cast demi onto Daiblos but I soon found out that almost every time Selphie's (and
whoever you picked for your third party member) draw would fail and I would end up wasting more time than anything else. So then I had Squall draw demi from Diablos and cast it onto him while Selphie and my other party member did the next best thing, summoned GF's and caste every kind of powerful magic I had. Diablos's Gravija attack will deplete each of your party members HP to Limit Break levels so then I caste Selphie's Full-Cure on everyone (you might have to use the O button trick or keep pressing Do over) and then started the whole process over again.
This may seem like a unsure strategy but with this battle I don't believe that there is a sure way to go about it. I cannot guarantee that you will not KO once or even several times before winning so don't let my decisions get in your way of your own. Experiment...have fun with it. (Yeah right...)
After you defeat Diablos he will join your party and give you his card.