Board Thread:Spoilers!/@comment-24674051-20150609161411/@comment-24674051-20150611145558

How about this one....

They go with the standard line where Mordred (aka the Black Knight) is the Bastard Son of Arthur and Morgan Le Fey. However, in this version, Mordred is not all out to dethrone Arthur, but instead has a fairly decent relationship with him.

When it is time for the initial tethering of the darkness, Merlin chooses Mordred (for good reasons), but Arthur gets upset and tries to stop Merlin from proceeding. When that fails, Arthur does something that messes up what Merlin was trying to do. (Possibly it is Arthur that steals the DO dagger from Merlin, and gives it to Mordred, so that he can be in control). And the story of the Dark One continues from there.

The only problem I see with this is how it fits in the Timeline. Arthur seems to be more contemporary, since we have Lance meeting Snow in the time before the Dark Curse. But the Origins of the Dark One would have to be many many ages ago.

And maybe the way to resolve this is taht the flashbacks are to a previous King (either a different Arthur, or perhaps Uther) to pick up the classic messed up family interplay, while the present day has a different Arthur that is more the leader of the Knights of the Round Table.