From the Kickstarter:
Dark Lords always seem to threaten the world. This time, that threat becomes real. Your fantasy world actually gets destroyed as it becomes another Planet Apocalypse! A unique new product for 5th Edition D&D, the Planet Apocalypse book provides rules and guides to turn any fantasy world into a post-apocalyptic landscape where the heroes fight alongside surviving remnants to stymie the fiendish hordes.
This full-color, high quality 325+ page tome includes subclasses, new feats, new spells new magic items, THREE adventures, a complete guide on what is means to bring the apocalypse to your fantasy world, 15 Arch Lords whose shadows literally manifest their own Hells, and a bestiary boasting more than 70 monstre stat blocks!