Regen

Regen is a passive ability featured in Kingdom Hearts Chain of Memories, it's remake and Kingdom Hearts 358/2 Days.

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 facimily of Halloween Town on Floors 2, 3, 4, 5 or 6. It last for 10 heals and heals quicker when HP is in the alarm zone.

Kingdom Hearts 358/2 Days
In Days, Regen is the effect of using the spell Cura.

Cura can be synthesized for 2000 munny once Roxas is promoted to Novice rank.
 * 1 Cura Recipe
 * 1 Cure
 * 2 Shining Gem.

Etymology
Regen is derived from the word 'regenerate'.