The Marks gold mines refer to several subterranean caverns artificially dug out and operated by Lawmen underneath The Grand Shrooms' stems. The sole origin of Stem City's infinite source of gold, a complicated process involving fire and pressure that has been developed over years in order to convert the massive stem's dripping sap into golden ingots. The carefully constructed bars are transported to and stored in The Complex after completion.
While this is an infinite resource, the rate of creation is incredibly slow. It takes days for enough sap to be collected for one bar, then an additional week for it to be forged.
All tunnels besides those connecting to The Complex have been caved in since Ahsonov's era.
A practice started by the Stems cult, the barbaric people once lavishly decorated their horns and armor with it. It was rumored they were told how to create it by their deity's gift, Stem Origin.
The extensive mines the cult constructed were lost to time until they were rediscovered by Stem City two and a half centuries after the cult's downfall. The benevolent off-world aliens helping the city build the Nexus took great interest in this infinite gold mine and the associated complex process of creation. They helped the Council of 12 replicate the lost process.
Seeking to make their citizens wealthy, the Council of 12 divided the old Stems reserves of the material into nuggets and handed them out. Once distributed, the people of Stem City started to use this gold as a currency. The council picked up on this fast and made it their official method of trading, each single nugget being referred to as a "Mark." Marks were born.
Once Lawmen were introduced to Stem City, the council wasted zero time in replacing their limited supply of miners by putting the robots to work. The council used their own portion of the gold to pay for things that their off-world business partners weren't openly trading with them.
Ahsonov came and went without touching the system put in place beforehand. The only thing he did was restrict those allowed in the mines to only Stem Tower staff.
The Complex and the XX539's DIGITALIZE ACT had the Marks gold mines all connected to The Complex's vault. Instead of Marks being traded physically, digital cards replaced the physical currency.
The STABILITY ACT of XX782 allowed Stephill Frie's company, BACKBONE INDUSTRY, to hire workers to help the Lawmen extract the sap. This position was taken advantage of by Mr. Frie to steal Marks gold bars right out from underneath his brother's nose.
Blema's DECENTRALIZE ACT tore away BACKBONE INDUSTRY's rights, successfully restoring the mining process to how it had been for centuries before.