Drain

Drain (ドレイン) is an ability found in Kingdom Hearts: Chain of Memories, Kingdom Hearts Re:Chain of Memories, Kingdom Hearts Birth by Sleep, and Kingdom Hearts Re:coded. It allows the user to absorb HP when attacking enemies.

Mechanics
In Kingdom Hearts: Chain of Memories, Drain is an enemy card effect that allows Sora to regain HP when striking enemies with attack cards, in exchange for enemies dropping fewer items. It costs 35 CP to add to the deck and lasts for one reload.

In Kingdom Hearts Birth by Sleep, Drain is a Dimension Link ability which allows the user to drain HP with every attack that strikes an enemy.

In Kingdom Hearts Re:coded, Drain is an Overclock ability that allows Data-Sora to recover HP when striking enemies with basic attacks.

Kingdom Hearts: Chain of Memories

 * The Search Ghost enemy card has Drain as its effect.
 * The Black Fungus enemy card can randomly activate Drain.
 * The Darkside enemy card can mimic an enemy's Drain.

Kingdom Hearts Birth by Sleep

 * The Maleficent Dimension Link has Drain as its level 2 ability.

Kingdom Hearts Re:coded

 * The Metal Chocobo: Ag and its upgrades have Drain as a level MAX Clock Ability.
 * The Ultima Weapon 〉〉〉 and its upgrades have Drain as a level MAX Clock Ability.

Etymology
Drain is a recurring Black Magic spell in the Final Fantasy series. It absorbs HP from the target to refill the caster's HP.

There are weapons and abilities in the Final Fantasy series with similar effects to Drain in Kingdom Hearts, such as Drain Blade.