The Eclipse Barrier (斬輝結界 Zanki Kekkai, localized as Zanki Barrier) is a unique type of Magic Formula that can only be performed by wielders of the Sealed Armament: Izayoi. Tsubaki Yayoi is shown to be the sole practitioner of the technique.
Somewhat similar to an Eclipse Field, the Eclipse Barrier has the ability to stop any interference with the world outside of it. This is one of the multitude of reasons that the Sealed Armament has gained legendary status, as not only is the barrier completely impenetrable, but not even Observers are capable of witnessing the events that unfold within it.
During BlazBlue: Continuum Shift, Hazama manipulates Tsubaki Yayoi repeatedly so that she may use the Eclipse Barrier and not be Observed by Takamagahara, meaning that they would be unable to immediately intervene and begin Observing a more favorable phenomenon of the Continuum Shift.
In BlazBlue: Alter Memory, the space created by the Barrier is shown to be pure black with specks of blue and white shapes, such as pentagons and hexagons, aimlessly floating around. There is also no visible floor inside the space.