“Dude this gun is awesome, I liked fighting that boss, I can’t wait for the turbo version”

You can make it so the length of time until they come back drops by half with every use, while they still get stronger… until it’s a boss sort of appearing in strobe light fashion while growing interminably up towards the sky, until one massive strobing hand slams down and squashes the whole party like a bunch of bugs. Fitting cap + end to the campaign