Arthur would never know. Merlin himself had made sure of that, and now after years of silent protecting and secret magic he was dying.
He had often wondered how he would die. He had had no doubt that he would die, but how he would die was something of morbid fascination to him. Sometimes he would fantasize dying for his king and friend, Arthur finally discovering the truth as his last breath passed his lips. But now, lying on the forest floor with a sword through his chest, it seemed a foolish fantasy indeed.
They were on a patrol, and bandits attacked. Merlin had been stabbed through the stomach from behind as he watched Arthur fight. That was it, so simple it was almost heartbreaking. There was no gloriously saving Arthur from a premature death by sacrificing his own life. There was no revealing his secret at the last second.
There was only a normal bandit, killing the king's servant because he had nothing better to do.
Merlin was detached form the pain of the sword. It came as too much of a shock, it seemed. All he felt was his magic slowly leaving him, and this was enough for him to fall into a state of calm acceptance. If even his magic knew there was no chance of saving him, than he himself knew there was no point in fighting it; in fighting death.
So he closed his eyes, and let go of his destiny for the first time in years. Who needs destiny in death, anyways?