Auto-Shell

Auto-Shell is a recurring ability that maintains a constant Shell status on the user. It is non-dispellable and will not wear off even if the user is KO'ed and revived in the same battle.

Final Fantasy VI
Auto-Shell is found on the accessories Czarina Ring and Pod Bracelet. Czarina Ring is only equippable by females. Pod Bracelet adds the Auto-Protect ability as well.

Final Fantasy VIII
Auto-Shell is learned on the GF Doomtrain. It can also be taught to any GF by the item Moon Curtain.

Final Fantasy X
Auto-Shell can be found on dropped armor or Customized onto armor by 80 Lunar Curtain.

[Final Fantasy X-2
Auto-Shell is an ability found on the Mascot Dressphere, and requires 80 AP to learn. The ability can also be accessed via the accessory Moon Bracer and by passing through the red gate on the Selene Guard Garment Grid.