I like the biblical undertones too, though they can go to far sometimes (Emma and The Last Supper for one).
I agree that The Dark One mythology needs more work than almost anything else and tying TDO into the fairies somehow would make me happy. Maybe they really should go back to the dawn of time and make Merlin the very first person (in this magical land at least). He escapes into this magical realm through a door or a magical pool in a wood or something and ends up in an enchanted and unpeopled realm. In that realm he finds the grail and drinks from it, becoming magical. He’s lonely so he begins bringing in other humans from our world to the magical realm. He thought this realm was unpeopled, but in fact fairies live there, and somehow the coming of the humans upsets the balance causing a fairy (either Blue or Black) to go dark and desire non-fairylike things. Then at some point Merlin meets Nimue who eventually drinks from the grail, becomes magical like Merlin and commits an act of murder which is forbidden in light magic and thus she corrupts her own magic and becomes the first Dark One. I still like that the dagger and Excalibur are two halves of the same blade, even though I think what they did with it sucked.
Basically both the story of the first Dark One and the origin of The Black Fairy needed to be set in ancient times and …heck they just needed to be epic and as written they just weren’t.
…you know I’m really enjoying this. It scratches some of those annoying itches Once has handed out over the years.