Soul Drain
Soul Drain is Aerith’s other starting ability, and it costs 1 ATB to activate. It inflicts a small amount of damage, and drains an enemy’s MP, restoring some of Aerith’s own in the process. If an enemy is Staggered, additional MP is drained.
While initially, you might not see a lot of use for this ability, it becomes crucial in the back half of a game. As the difficulty ramps up, boss encounters become grueling battles of attrition designed to be a test of your resources and being able to gain MP in this manner is a godsend.
Be sure to use it whenever you stagger a powerful opponent to receive a substantially larger amount of MP. Think of these moments as a reprieve to heal and recuperate, in addition to being the moment to launch a counterattack.