Phenom 4 and the Phenomena Myth

Once upon a time, a band of adventurers (?) managed to stumble upon the world of Phenomena. Maybe they were meant to, and maybe they weren't.
You see, at the time, they weren't classed as Adventurers, and there are plenty of questions as to whether they ever were Adventurers. Rumor has it that they were a team of highly trained and organized specialists, an elite squad of the Black Plague, those unholy terrors on the leash of the Lich Kings of Nula. In time they would come to be known as the Phenom 4 and, I believe, responsible for opening a door that no one had any idea they should have opened.
Phenomena? Well, it's said to be a magnificent world in the Out Yonder cluster. But it's difficult to get to, lots and lots of dangerous things there. If you manage to make it there, there's a temple on a high mountainside in the central continent. Looks like a pyramid and it has a large hole in the sunward face. The Phenom 4 got in there and got hold of some sort of crystals and Lumina knows what else.
But I believe they're the reason why the Necrocracy is as powerful as they are, but nowhere near as powerful as they'll be. And that level and kind of power spells death for a lot of people, maybe all The Folk.