In another roleplay venture that exists now elsewhere, I attempted to create a science fiction setting with a fantasy twist. I didn't just merge them, though; I spent hours and hours analyzing what created the tones for both, the themes, interaction styles, plot types, tropes, so on and so forth. My clear goal was to capture the successful and poplar fantasy archetype but sculpt it into another genre that made it work. One of the things that helped me achieve this was how I addressed magic, if you can call it that. In the world, magic and mutations existed side by side. Essentially, all inhuman abilities were ways of manipulating a fictional elementary particle, informally called Ley (because it was thought of as mana, or energy, and never so formally researched to be given a name). Ley itself had no true mass or unit of measure; as long as requisite materials were available (more ley), it could absorb or disperse Ley. It could change its charge at will. It could, with perfect efficiency, transition between wave and particle, where all of its traits could be as easily altered as they are as a particle. Ley, in essence, could fulfill the role of any sub atomic particle or form of energy, and Ley was capable of being manipulated by living beings. Whether it was through magic, mutations or both, the manipulation of Ley and later Ley-Lines (massive, vein like structures of Ley inside the Earth) acted as the scientific explanation for mutations while also opening the doors to all sorts of mechanisms for magic. Mutations were a line in between. Magic itself was so rare, as fact, that mutations were considered the only way to control Ley, and even then people didn't just "know" about it - it wasn't treated as common knowledge. Characters grew up in a post-Apocalyptic world that went on to become something else hundreds of years after the old world's fall. Mutations weren't "explained", they just were; all of this knowledge almost never actually seeped into the narrative, and that's why I love it. As people, we went tens of thousands of years existing in a world where we didn't really know about physics, and I think recapturing that in a roleplay made this single creation my favorite. It acts as a guiding force, a fundamental principle and a powerful tool for explanation while rarely coming into contact with characters. The explanation I have for it is so broad that there's essentially nothing that it cannot explain, so what I can allow players for creativity is limitless. The limitations then became the theme of the roleplay and because I could work on preserving the original theme I had in mind, creating a fantastical, post-Apocalyptic science fiction setting was made a whole lot easier.