SPIRIT VEINS

Most of a planet's helium is produced when coincidences or unlikely situations occur within the planet's crust. This makes the gas very rare. Extracting helium from the air is highly uneconomical, yielding less than 0.00052% in air.

Wait! How could my citizens understand what helium is? Oh! Okay, I see... Leonardo da Vinci is at work here. It will not be a problem for my citizens to learn new knowledge.

"What else?"

Mystica picked up the next stone tablet. She saw the boldly written word on the stone tablet.

Coal

This resource, coal, is a fossil fuel created through a process known as 'coalification'. Plants formed millions of years ago in swamp forests died and formed layers of peat that were buried through geological processes, which gradually changed to coal under intense heat and pressure in low-oxygen environments.