Drain HP from surrounding enemies.Description
Spirit Siphon is a new Enemy Skill ability, which did not appear in the original Final Fantasy VII.
Phantoms are first fought in the sidequest "Missing Children" in chapter 14, "In Search of Hope". They use Spirit Syphon randomly, and there are plenty of opportunities to learn it. Spirit Siphon is learned by sustaining damage from the ability on a character with Enemy Skill equipped. Doing so only provides a chance to learn it, however, and this may need to be done multiple times.
Spirit Siphon can restore HP from many nearby enemies. Because it is a medium-range ability, it is best used by Cloud and Tifa, since they fight in melee range. Spirit Siphon's main use is in hard mode, as it is an MP-efficient way to both heal and damage enemies at the same time. Pairing Enemy Skill with HP Absorption Materia can amplify its HP regeneration even further, which is an efficient use of slots as HP Absorption is an effective combo with other Enemy Skills as well.
Similarly to Soul Drain, using Spirit Siphon on undead targets will inversely restore their HP and damage the user. Tifa can use Starshower to improve the damage it deals, also allowing restore more HP, especially when paired with HP Absorption. However, doing so requires Refocus, due to it’s 2 ATB cost.