All he could feel was anguish. Betrayal. Heartbreak. Arthur felt that feeling. The feeling of breaking at the smallest inconvenience. The snap of a twig, a twitch of the saddle, it made him want to crack open the skull of anyone who dared come near.
Why would Merlin do such a thing?
Years of faith. Of trust. Clearly they fought, playfully. That was the entire bases of their (rather rough) relationship.
Arthur may have kid around a bit, occasionally taking it a step too far. Too real. But it was always with good intentions. No matter how hard he tried, Arthur would always appreciate Merlin. After what seemed like centuries of council and friendship, how could Arthur not?
Centuries of trust.
The death of his father. The destructive effects of his uncle. The utter hurt of Morgana.
Nothing was as devastating as Merlin.
His confident. His friend- more than that. The only one that truly knew him. Who may have called him an ungrateful prat from time to time, but never lost faith in him or his destiny.
The destiny they shared.
His father had always warned him to never trust anyone. That trust was never well placed. Trust led to disappointment. Trust was for those who were weak, and needed help. Arthur always believed Uther. No matter the consequences. He would protect his father's honor.
How could Arthur even blame Merlin for his secrets? Why would Arthur have the right to judge, when his own father slaughtered sorcerers?
The very thing Merlin was. Down to his core, he was a noble warlock. The most powerful warlock.
At Arthur’s mercy.
It was then that Arthur calmed down.
Now it was disappointment that haunted his nights. Disappointment in others. Disappointment in himself. Disappointment in the very fact Merlin was unable to trust Arthur enough.
It came along with his anger. The fist of fury that hit him like a truck. Arthur went right past grief, head first into something that paralysed his most powerful enemies.
Blood boiled. Flesh reddened. Eyes narrowed.
It made his pure soul malicious. Made the wise king do horrible, wretched acts of violence. He would destroy any adversary. Raze his opponents. Level any challenger.
Arthur's chest tightened. He felt choked off. His throat was heavy. A knot constricted around his Adam's apple. His eyes filled, but nothing was released. Not a single drop was spilt, nor was a breath missed.
How could Merlin betray him this way?
That didn't matter. It was too late. Years of friendship built, and in the end Arthur would never.
He would never not believe in Merlin. In Emrys.
Merlin was selfless. He had never taken credit for his marvelous actions.
Arthur would always trust in him. No matter what.