Regen

Regen is a passive ability featured in Kingdom Hearts: Chain of Memories and Kingdom Hearts Re:Chain of Memories.

In Kingdom Hearts 358/2 Days, Cura has the same effect as Regen.

Kingdom Hearts: Chain of Memories
Regen appears in the form of a card: The Oogie Boogie card. It is obtained by defeating Oogie Boogie in Castle Oblivion's facsimile of Halloween Town on Floor 2, 3, 4, 5 or 6. It lasts for 10 heals and heals more quickly when HP is in the alarm zone.

Etymology
Regen is derived from the word 'regenerate'.