User blog comment:MerlinUSA/Merlin -- The Big Picture/@comment-5764349-20130116222339/@comment-5995315-20130117023031

What the Dragon said (in the first episode) was that Arthur was destined to become Camelot's greatest king and bring about Albion. He told Merlin that Merlin's fate was to protect him. When Merlin said he didn't see how this Prince Arthur could change into so great of king, the Dragon told him that  it was Merlin's destiny to bring that about.

The next 64 episodes show, each in its own way, just how this occurred. It wasn't through action so much as personal growth. By Season 4 Arthur demonstrates greatness in his decisions (4x5, for example), and by Season 5 great wisdom (5x4). Along the way he learned to temper his masculinity with intimacy. So when he died, he died knowing Albion was safe (Morgana was dead) and that he had known great love and now felt intense gratitude as well toward Merlin. He had no further ambitions and could now die in peace.

The finale leaves no reason why Gwen couldn't have allowed magic, but the Disir episode shows just how tricky it is. Arthur could not have accepted magic on the Disir's terms and remained a great king. He would have been a  slave to whatever evil the Disir had in mind -- they said so themselves -- and he would have exposed his people to extreme danger. His refusal was wise and responsible, even if it was fatal. That's an example of great leadership.

As to Morgana, Katie McGrath has said several times that her character stood in no need of redemption in the first place. Morgana and Merlin both readily embraced their fates in the finale, despite whatever initial reservations they may have had. This goes back to something the Dragon said, but I'll post about that later.

Season 5 episodes make much more sense that they seem to at first. This is why watching the finale again might be helpful. The episodes are complex and thought-provoking. I don't think the season stopped making sense simply because it took a serious turn.