Save file idea

I could imagine a game that gives you a save file mechanic, and you can have up to 99 save files, but in doing so the game hints and warns you this'll make the final boss even harder to defeat, and once a save file is created, you cannot delete it: only save over it, essentially setting your save file in stone. The save mechanic would be an alter, or a forbidden book, at the final fight the boss would be able to take away all your save files except for the one that has the most progress, and burn them to increase his / her power, each save file being a LV UP for the boss, how many times you saved would also power up the boss and make the AI smarter.