We saw the first knights in Alpha. [scryfall]White Knight[/scryfall] was a strong and efficient card by the standards of those days and still is for an uncommon. But there was also it’s dark counterpart, the [scryfall]Black Knight[/scryfall]. A flavor-win certainly, except that of course they could never actually fight due to their Protection abilities. Both saw some tournament play (I certainly played with both back in the day) and both have seen a number of reprints. White and black have also been pitted against each other in a similar way quite a few more times, often through knights.
This is specifically for white and black. There are other similar mirrors in white and red, but we’ll forget about those. Since the mirrors don’t sometimes come to be in the same set, I’ve placed these mirrors where the latter part was first printed. White has plenty more knights than this, but we are specifically interested in these pairs here. Black has some other ones as well, especially in Ixalan, but again, not interested in those.