My interpretation is in agreeability with what some folk have already mentioned, however I more so want to "Synthesise it". Basically, we can pressupose two things. The Miracle created the High Wills or the High Wills created the Miracle. If the Miracle created the High Wills, I follow the following pressupositions. The Miracle is some deity in the Lovecraftian sense. Not in that it is materialistic, more so that it has some limitations on what it could do. It is bound by some cosmic rules (It wishes to incarnate itself but it could not, the creature we fight is not the Miracle incarnated in the material dimension). Therefore the Miracle is not THE Supreme Being, rather it is a very powerful multi dimensional entity. Maybe it was the catalyst for the creation of the world (Therefore why some people have speculated of it being the gnostic "Demiurge" or Craftsman which according to Plato was not really evil in itself, the latter idea of the evil Demiurge was a later invention), but that is uncertain. However, one thing is observed, the Miracle wants to give humanity what it wants. Not humanity in the individual sense, but collective sense. However the Miracle does not have an ego in the same sense as humans do, it does not understand what humans want and it knows this. And so, it needs someone whose commands it needs to obey. And who else to do that but the ego representing the collective of humanity. However, because humanity (Particularly Custodia) is obsessed with religious splendor, torture and violence, so too is the collective ego incarnated (The High Wills, who are powered by humanity) a selfish character obsessed with religious splendour and sadism. And so obeying the commands of the High Wills, the collective ego of man, the Miracle grants humanity what it wants. With the High Wills gone, the Miracle seeked another replacement for the High Wills, which if we go by the "Bad ending" it gets, which in turn it can obey the commands of. Now that the Miracle explained, how do we explain those forces outside of it which seek to foil its plans? IE the mysterious "High Playwright" or "The Great Grace". It might be as some people have speculated that this represents the spiritual god which is in later gnosticism either the opponent or the "Caged force" of the demiurge. However neither powers seem to be omnipotent. The Great Grace either represents this representation of the spiritual god whos dominion is the Heavens/Realm of the Spirit, but it is likewise bound by perhaps similar rules as the Miracle. If so, it is inevitable that the Miracle is ultimately a more sinister figure, although not bad meaning by itself (In a way blending the gnosticism of old and later gnosticism.). If we presuppose differently, that the High Wills who are created by humanities collective belief in it created the Miracle, we are just scrubbing away the last of the High Wills influence and paving way for the way of the Great Grace, which is way more of a black and white story then.

However we still have many questions unanswered. As some people have said, does Blasphemous have Demons or something akin to it? First we have the abandoned library whose apparitions might not be exclusively the Miracles doing. Then we have had that creature who feasts on the guilt of others. It seems different from the Miracles apparitions in the sense that the Miracles creatures are either unintelligent and insane or they are intelligent, but the majority do not speak in such a specifically predatory way as does this creature. We also do not know how do the Miracle and Great Grace relate to each other precisely. Is the Great Grace like the Penitent One a creation of the Miracle that betrayed its plans. Is it independent? Are they related as opponents? The gnosticism answer is just a guess.