an alternate universe in which Merlin eventually loses it after waiting for Arthur for so long.

He watched Camelot fall. He waited and waited for so many centuries. He witnessed many disasters rampaged the world, yet Arthur was still in his slumber. He started doubting if Arthur would wake up at all, and that was the start his ruin.

Immortality eventually destroyed every trace of the kind boy he once was. Madness and loneliness consumed him. The guilts he had carried for thousand of years took him apart. Eventually, the only thing that was left in his monstrously powerful and everlasting body was pain and glimpses of memories of Arthur.

And finally, Arthur was back as the ‘hour of need’ finally arrived, as the world needed him to save it from the destruction that was once Merlin.