Tralphium

All fusion cores in the developed Old World were based on tralphium, or Helium-3 fusion. This technology had been developed for centuries, making the cores smaller and smaller and the conversion efficiency higher. Every modern spaceship had a Tralphium core and a mining extension to make the ship self-sufficient for long travels. 
This was true for the original settler ships as well. They had sufficient fuel for many more years of travel and high-end reactors that would make most of the Old World green with envy. Why and how did a few thousands of them get a hold of such ships is something of a mystery. When the settlers finally discovered their new promised land, far away from the usual galactic routes, in the unpopular and rarely visited sector, they had to put these gems of technology to a different use.
Ships were completely dismantled and repurposed as energy sources for the developing cities. Even though the reserves of tralphium were substantial, they were not infinite. The amount of He-3 in the atmosphere of Garuda were abysmal, making the harvesting efforts almost fruitless. With the ships dissembled and their parts recycled or reused, there was little to no hope of future space travels on a planet with almost no metals and no fusion fuel.
Strict conservation of power made Garuda one of the most grotesque worlds in the history of humankind. Cutting edge reactors providing energy to the greenhouses, research centers, terminals and the necessary common network, but on the other hand no artificial lights in the homes or the streets, and no power sources for civilian use. The fields are worked manually and with primitive vehicles to this day. Even the irrigation system, which is the heart of the settlement, is an elaborate mechanical machinery that depends on gravity, levers and corkscrews rather than electric power. 
When Pon Osni made his revolutionary discovery - that Garuda is actually a moon orbiting a gas giant, the exploration of the Bright Side became the question of survival. If this gas giant had an atmosphere rich in He-3 his fellow Darksiders would be settled forever, even able to travel again. This was the start of a new era in the history of the Dark side, and a beginning of a two-centuries long cold war.

Type

Elemental / Molecular