Zainia. Its in my valued resource part. Basically what I thought of it as is a mineral/element with a super special property. Its atomic structure allows it to have a sustained fusion/fission reaction with clumps exceeding 100kg in mass. What happens is because of its structure, once it reaches a specific temperature it undergoes a fission process, this fission reaction heats it up even more, creating a fusion react, recombining the just split atomic structure. After a few seconds it cools down to the point where the fission reaction restarts, and so on. Its ridiculously hard to find, extract and contain. (its only found near the brim of the mantle of the planet, the heat there is what even starts the fission reaction.) The sentinels use it to power ships, cities, and its plasma weaponry.