Eternal Order of the Second Death

About the religion
The Eternal order of the second death is a polytheistic religion led by Gary Miller.

It was founded in the nether and it is centred around the being called UNSPEAKABLE and „the second death” which is a ritual that will give the user immortality.

How did the Order of the second death end up in overworld?
The Order ended up in the overlord thanks to (or because of) Gary Miller a being of unknown race which got somehow got out of the nether.