Wow. Those are some pretty amazing spoilers.
"In robbing him of his magic you have lost yourself ** ****" ----> to evil? No, I think "an ally" might be right, BM. Maybe the ally is Aithusa?
"We can only be grateful she failed" Could this be someone talking about Morgana having failed to kill Merlin?
"Let her go, she is not your enemy, I am" This one totally has me puzzled.
"Those are not the values that Camelot was built on" Well, that's obviously Arthur.
"A ****** worthy of my proudest warrior" ---> weapon? Could this be Morgana, about the dragon-forged sword?
"I always thought you were the ******* *** I ever met. Guess I was wrong" ---> bravest man? Oh, ouch! I think this is the severe left turn: Arthur finds out Merlin isn't going to the battle with them, and he gets nasty.
"If I find what I'm looking for I will perfectly safe, I promise you" Merlin to Gwaine, maybe?
"Then there is nothing more to be said, except that whatever it is I wish him luck" Arthur, about Merlin going off to find something (his magic)
"I have no reason to go on, the battle is already over, Morgana has won" Probably Merlin, wanting to give up after losing his magic.
"Move towards the light, your destiny awaits" *jaw drops* Um... Balinor? Wel, as long as the light isn't an oncoming lorry...
Trailer Teaser "I am a ********, I **** *****" ---> I am a sorcerer, I have magic? I know we all hope it's Arthur, but this is probably to Gwaine or Guinevere