Arthur's legendary battle at Camlann became an inspiration for the name of a world famous royal castle known today as Camelot, although the name of Camelodunum as the once capital of Roman province of Britain is also one of many possible explanations. See more
He was a loyal soldier. In robbing him of his magic, you've lost yourself a powerful ally.
Perhaps, but now we know the war can be won, for Arthur is nothing without Emrys, and Emrys is nothing without magic.