I don't know if you know alreadly Know how to defeat Diablo but I will tell you!
You know that diablo is in the lamp.when you wanted to beat him remember to save and buy lot of potion. And you must also has some characters in your group how to draw and use magic.
Like this:
Squall
Attack
Magic = This one
Draw
Item
You will know that diablo has Demi. First Draw demi on him.After you draw it cast it on your magic. Remember is Magic not draw. After you had cast it on your magic
Diablo will Curaga you. Do it like this until you damaged him for aboout 200-1000 like that and you use your weapon if you like or keep using the method.
Remember Draw first and cast Demi back on Diablo with you Magic.
Did you know about the Squall Strongest Weapon LionHeart and how to get it?
If you did not know tell me and write it down on the Supercheats (ASK A QUESTION) on the final fantasy VIII and if I see it I will answer you back!!!