The Immortal Breaker (不死者を倒す兵装(イモータルブレイカー) Imōtaru Bureikā, Undead-Defeating Armament) is a weapon capable of harming immortal beings.

Gallia Sphyra: Outseal is an Immortal Breaker. It is a Legacy Weapon designed by humans during the Prime Field War for use against the Prime Fields. As a result, it was given the ability to harm immortals.

Mai Hazuki used Outseal in BlazBlue: Variable Heart against Fuzzy, which harmed him, as he is a vampire and thus immortal.