Was Felix actually qualified to learn the Phaeron Codex? Why? How was that even possible?

As someone who practiced the Red Moon Reincarnation Requiem, the Scarlet Lord had faced all kinds of enemies. Even when he couldn't win, he could usually survive. There was one exception—someone who could cultivate the Phaeron Codex. That was a threat he couldn't possibly contend with.

However, the Phaeron Codex was nearly impossible to find, let alone master. On top of that, its cultivation requirements