Merlin now knows the future but cannot change it. That's the core tragedy of Season 5 — the hero is trapped by foresight, forced to walk toward doom.
He loves you, Gwen. I’ve never seen him look at anyone the way he looks at you. Not even... well, not even a pile of gold. merlin season 5 episode 2
Love is not enough to save a kingdom, Merlin. But perhaps... perhaps distance will give him the clarity he needs. Merlin now knows the future but cannot change it
The prophecy says: "The bane of Arthur is the druid boy — he will tear down the walls of Camelot." Everyone (including the audience) assumes "bane" means enemy/destroyer. But by the episode's end: I’ve never seen him look at anyone the way he looks at you
I have given the order. You are to be exiled. You are to leave Camelot and never return. It is the only way to spare your life.
But deeper:
The biggest talking point of the episode is undoubtedly the re-introduction of Mordred. No longer the young boy Merlin once protected, he is now a skilled warrior played with chilling nuance by Alexander Vlahos.