Infernal Abyss

Fight your way out of hell. The Solar Rune has weird properties, especially that of it's rebirth one. It's so hot that nearby rock gets melted into magma, and that magma attacks living creatures seemingly on purpose, and then those living creatures re-awaken as walking ashes and various other demon-like creatures. It's been doing this for god knows how long, and once it has an army large enough, it will bring apocolypse to the world, the hottest summer of man-kind.