Grim Depths

Battle your way through a dungeon, then upgrade and unlock new gear (Like the "Satanic Blade," a giant sword that burns enemies or a staff that launches lasers to kill a whole line of slimes at once) by spending your life at a demonic altar which also re-colors the entire game, and then enter the next dungeon, with stronger, faster, and deadlier enemies, battling your way from the first demonic red dungeon to an acid-green dungeon all the way to the final glowing white dungeons.
https://www.youtube.com/watch?v=_4wqyXQlQ4I