Well, thanks for your quick answer ! I have read this walkthrough and it really helps to spare time. But for the last fight, it doesn't. The problem remains the same and though I summon Faahlda (who stays for 10 rounds) I cannot destroy the "Fire" malisphere. My last "fire" attacks are made against Alexandria and don't hurt the last malisphere (once I succeded in inflicting a few points of damage) and finally all my SP are gone. I have the best level (99) and probably the best arm, armor and items with diamonds everywhere. Of course, the end is the bad one after an endless and boring fight.
Should I operate with an other tactic ? Maybe Faahlda must be summoned at a special moment ?
Your advices are welcome. Have a good day !