Centuries had not dulled the sharp pain of losing his best friend.
"Only for you, my lord," Merlin had vowed, wincing at the horror and betrayal in Arthur's eyes. He had almost wanted to laugh – after years of hiding his magic, the one time Arthur catches him is when he is trying to finish a litany of chores. "I swear, my magic is for you and the good of Camelot only."
Arthur decided that what was best for Camelot was Merlin's banishment.
Merlin never really left. He protected from afar, intervening whenever his king was threatened by magical and nonmagical foes alike. Whenever a particularly stroke of good fortune occurred, Arthur would close himself off from everyone else for days, cold and distant. Merlin would watch, knowing he was the one who broke the king's trust.
But Merlin comforted himself with the fact that Arthur never betrayed Merlin's secret. Arthur told the others he had drowned in a river during a bandit attack. No questions arose, though Gwaine punched Arthur hard in the jaw and left the king's service.
Right before Arthur died, he finally forgave Merlin and accepted him for who he was. Even so, Merlin never used magic again. Instead, he released the built-up energy into the earth and the ruins of Camelot became the richest forests ever known, guarded by thick layers of wild magic.
As the years passed and everyone he knew had died, Merlin retreated into the woods to await his king's return.
No matter how long you take, I will always be here.
This is my first attempt ever at writing fanfiction, so please review and let me know if I'm doing anything wrong!