PROTOCOL:EJ is a special protocol made by Foster Forfant, with the assistance of a mysterious Gatekeeper. It was created with the goal of killing Joseph and Josh in order to secure control over the world of HoEP. Not only is the device itself required for this, but the Mirror of Reality, along with all twelve of the Sacred Gemstones, is also required.
Not only can it be used with the mirror to erase Joseph and Josh from both the real and anime world, but it can also be used to power up GOD, a powerful weapon that can send up to twelve victims into life force paralysis, or it can be used to kill one person with a single, seeking shot.
The device used to power PROTOCOL:EJ is never actually seen, though its core is, taking the form of a warped crystal. The device supposedly has a design based on the Mirror of Reality.
Relevance to the story
PROTOCOL:EJ was created by Foster Forfant in order to get rid of Joseph and Josh, however, it cannot operate without the power of the Twelve Sacred Gemstones. This causes the major conflict between Foster and the Union of the Sacred Gemstones, since both wish to acquire them.