This is a spear capable of killing those outside of reason. Its utilization requires removal of its restraints, after which the user has to pierce the target with its blade. At that point death is placed in the target's mind.
This ability was used in the series on two characters. Firstly, it was used on Jin Kisaragi, but the Immortal Breaker was nullified by the Power of Order and the blade didn't pierce him. The second time, Hades: Izanami was stabbed by the Izayoi blade, but it didn't work, as Izanami is the death herself.
In BlazBlue: Chronophantasma, Tsubaki Yayoi is tasked with utilizing this ability against Rachel Alucard, at the request of Rachel herself, in case that Ragna the Bloodedge isn't slain before his natural death.
The activation code for the Immortal Breaker:
|“|| Releasing weave restriction zero... "Immortal Breaker", activation. (零織拘束具解除…「||”|