Omake: The Crystal Matrix
@Questor
The helms that every crystal pony save a few wore was in fact not that complicated magically speaking, it was originally developed before Sombra's rise as a means to help Ponies with nerve damage to trot again. Sombra took this invention of a doctor and warped it to his own ends. During his reign of terror he placed the helm on one of the captured nobles and commanded her, to corral other nobles. It failed rather spectacularly as they would never stop corraling, and she simply corraled the entire city running all the way out of the the empire, prompting Sombra to kill that entire collection of nobles to ensure no news got out about it.
Mind control, Sombra realized was possible but limited, the instant he was distracted the pony would have freedom and couldn't be trusted. So... he took some magical crystals, and encoded a link between the helm and the crystal. This worked... partially. Sure the pony was dominated, but given no commands, they would simply stand until they collapsed. So Sombra went back to the drawing board, there must be some way to encode commands into the crystal for the pony to perform without his direct input. Sombra was distracted by the last stand of the Crystal Praetorians but returned to the Domination Helms afterwards, and as luck would have it going through Crystal archives from before the Age of Discord revealed to Sombra, the unquestioned ruler of terror in the Crystal Empire, a book. A book written by Crystal Pony Princess Silver Lovelace, on a mechanical language based on binary mathematics, a coding language. Torturing a Professor at Crystal University's family, made a stallion skilled in such knowledges pliable to their instruction. Binary mathematics, led to Basic code languages, led to more advanced scripts. With every terrible advancement in coding came other requirements. The crowning glory of which was the Crystal Matrix, Sombra's most advanced magical artifice, far beyond the golems.
More testing yielded by Sombra realized he could use the helms to get compliant subservient workers at efficient economies. This pleased him. The first crystal ponies dominated by the helms were miners at the mines. Once enough crystals were mined, Sombra placed domination helms on the Crystal unicorns, forcing them to do the painstaking fine detail to encode complex codes and commands for the domination helms. Within a year... a third of the crystal populace were wearing domination helms... After another uprising to stop Sombra failed, as they were unwilling to fight the dominated ponies. Sombra laughed darkly that he forced soldier commands upon the captured families of the resisting soldiers. Those weak willed fools didn't have the will to kill their own families to oppose him.
After another year there was no meaningful resistance, domination helms were on ALL ponies from infancy. Sombra was pleased at his own work regarding the Crystal Matrix, the interconnected command terminal for the crystal ponies, so pleased in fact he commanded his nation to applaud him for it, and soon the crystal ponies returned to their assigned task as dictated by their scheduling scripts. Without having to dominate the will of everypony himself, Sombra was free to do other things, like make golems or commune with Windigos.
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Years passed, and the helms remained in operation, but deep in the bowels of the Crystal Palace, the bureaucracy kept functioning for this Imperium of Sombra's. All Empries had paperwork after all. One dominated pony dutifully received a report at their desk, but it was placed askew on their desk. The pony's subconscious knew it was odd, there was no beating the script that blared throughout her conscious mind day in and day out, but crystal ponies could push in very minor ways. The most she was ever able to manage was placing a form upside down, or a few typos which the system didn't rat her out on. As a result seeing an askew paper on her desk didn't happen unless the dominated clerk forced it to be left askew.
FORM COMPLETE, PROCEED TO NEXT FORM. START SECTION 1
The pony picked up the form and began to read... This was a blue form, filled with typos, scratches and miswritten text. This perked the subconscious mind's interest, at least 8 ponies all dominated tried to make errors on this ONE form. She mustered as much strength to help the fight as she read
The dominated pony knew what had to be done to this report, what the script demanded of her, and what had to be done. The number of errors, how many ponies had pushed their mental subconsciousness this far to make errors. This report had to be destroyed. ALL Crystal ponies knew it who even glanced at this, but the scripts blaring in their head wouldn't let them just destroy the report. Everypony had done the limit of their power to, and now it was up to her.
PROCESS FORM. FORM CORRUPTED. OPENING SUPPLEMENTAL ASSISTANCE NODES
...and like that she realized she had a free hand... partially, just to help process this form. The great Crystal Matrix, the master computer that Sombra forced all ponies to processthrough had a bug... a bug Sombra wasn't aware of. When the script wasn't able to determine what to do it opened up the subconscious to control and assist due to the helm's design. It was an undocumented design feature of the first helm designed before Sombra's takeover, it allowed doctors and other unicorns to assist in helping physical therapy. Now? It was the only respite besides unconsciousness that was the cells of their own minds... and now she had it. This is what the other ponies before her were trying to do, create enough junk data on the form so that eventually the Crystal Matrix would release one pony just enough will to help it comprehend. Something she had no interest in doing
She grabbed a form from her desk drawer, a notice of an auditor's report being illegible and requiring resubmission... next decade satisfying the script partially. The damning form which was the only ray of hope that the crystal ponies had, was pushed into the shredder.
VIOLATION: Demerit 37 of 100. Un-Permitted destruction of Assets 75 points added. Exceeds threshold. PUNISHMENT: Death.
She welcomed oblivion as the electricuton process began, and no one would ever know what that form was, just a missing piece paper. Hopefully one day her people would be free again...
>>>>>
So this is what I come up with after playing Papers Please. I reason that there is no way that Sombra could keep all those mental control spells himself, or enchant each helm to do precisely what his empire requires. He would need a way to swap out commands without using his own magical power. So... he gets the crystals, encodes a mindcontrol script into a crystal that links the helm to the crystal. He then puts the crystal into the Crystal Matrix which allows him to in effect program his populace like one would computer code. It's monstrous, but I figure what else can one expect from Sombra.