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Ocularis Infernum.

The Ocularis Infernum (Latin for the "Eye of Hell") is an eye located in Hell that, once opened, will allow its user (whoever it is that is able to control it, that is) the power to see everything in the past and future, Heaven and Earth, the blessed and the damned.

Basileus's Machine was designed to open the Ocularis Infernum and give the machine's user control over it by using the ghosts of the Black Zodiac. However, once the machine was destroyed, no one could access the power of the eye.