I have a piece of merlin buffy crossover fanfic.
which was mostly inspired by this. Because the two shows have a main actor in common (whichs makes crossovers a little bit more fun in my opinion) Antony Stewart head played Uther on Merlin, but a few years before that he had the role of Rupert Giles, buffy's mentor on buffy. He knew magic too, he was powerful enough to go up against the big bad of the sixth season in a magic duel.
So I half wrote a story where giles accidently gets sent back in time, and starts destroying magic books to stop that big bad from rising.

(basically the reason I will never take uther's hatred of magic seriously)