Okay, I got every upgrade for every character and used all the runes. I've played the Boss 9 times now. Every single time he gets to 1/4 health he one-shots me, I revive and about 15 second later he one-shots me a second time.
Maybe I'm missing something, but I ground out stage 14 at least fifteen times to get all the upgrades and I still can't beat this game.
If you want a game you have any hopes of finishing, don't bother with this one.
 "Mighty Knight"){kind=icon}