Read the other comments dude, we don't know what if anything Shwig's planning them for. A couple of people, either paying money or who are friends with Shwig, are discussing rules and balance, but we're still in the dark for solid context.
Sup guys, I'm the guy who commissioned and came up with the latest six of these knights. Shwig's taken a few liberties with my designs, but the spirit is captured well and I'm pretty damn happy with them on the whole. Let's all give it up for this kickass artist!
As the kind of game, if anything at all, isn't known at this point, rarity and unit cost might actually be a way to balance their power. If you've ever played fire emblem, there are some powerful characters that don't really grow as the game goes on.
You guys are correct, the power creep is getting a bit out of hand. It's why I'm planning on going over the old ones with shwig to make some improvements (and also to fix the hundreds of terrible typos I made earlier on them).