HP Absorb (ＨＰきゅうしゅう, HP Kyūshū?) is a recurring ability in the series. It generally allows the user to regain a small percent of HP upon damaging the target. It is similar to the abilities Drain and Vampire.
The Blood Sword has this ability. The damage cannot exceed user's max HP minus their current HP. The user is healed for an equivalent amount of HP when attacking.
HP Absorb is a Support Materia that restores the user's HP when the paired ability is used. The amount restored is 10% of the damage dealt, but if the ability heals the target, HP Absorb will hurt the character instead. Linking HP Absorb to an attack that does damage overflow to a target will kill the attacker.
When linked to Magic and Summon Materia, HP Absorb will apply its effect to all abilities the Materia grants. When linked with a regular Command Materia, HP Absorb will apply its effect to the ability that is highlighted on the Materia. The darkened ability will only gain the effect if the character has another source for that ability; for example, if a character has Level 2 Throw, which grants Coin, the HP Absorb applies to Coin only, and not Throw, unless the character also equips another Throw Materia at Level 1.
When linked with Master Command, HP Absorb will apply its effect to all commands in the Materia, plus the Attack and Item commands (Throw is exempt unless the character has another source for the Throw ability, since Master Command doesn't support Throw as a separate ability). Equipping HP Absorb with Master Command allows the character to gain HP for performing regular attacks, but using healing items and magic will add damage equal 10% of gained health.