My friend and I used to play pretend. We imagined this huge world, with many different races and cultures, though the main focus was on a continent divided in twain. In the north were the forces of good. Good men, wood elves, high elves, dwarves. In the south were the forces of evil. Evil men, sand elves, orcs, trolls. There were neutral people too. The men of the west (basically aztecs across the sea), sea elves, the northern raiders (vikings). There were a bunch of different schools of magic, each basically created around an "element". It started out with basic things like fire, water, air, super basic natural stuff. We added in more like sound, darkness, ice, sand. And eventually there were the ridiculous ones that were more or less as a joke, such as nuclear. A lot of it was heavily influenced from fantasy and other media we consumed (LotR, Eragon, Runescape). We started pretty much when we met when we were 8, and it kept evolving (admittedly shamefully late) until we were in High School. It was a lot of fun.