Doubt
He was not like any villain you have ever faced Twilight. He is physically weaker than nearly every creature actually and in that regard he is not dangerous. Additionally he does not eat any living creature be it animal or plant, surviving off a chemical concoction he refers to as Soylent. He is however, dangerous to nations and stability. According to him we are agents of order while he is an agent of freedom.
It started out simply enough he came before me and my sister seeking to know why he couldn't see the sun and wanted to be pointed towards an academic to aide him to that end. Interestingly enough he was not blind, he used a torch to light his way; it truly was just the sun and its light he could not see. We told him there would be nopony more knowledgeable than us on the subject of the sun and moon. We told him what everypony knows, about how we raise the sun and the moon. He already knew of this tale before gaining an audience with us and hearing it from us he asked if we truly believed that tale. Naturally being what we have done for ages we told him as such. After asking about before our time and learning of the struggle between the three pony tribes, he was silent for a time before he vowed to gather evidence that would prove there was no reason to lie to him about what he already knew to be the truth.
Over time he did just that and those he got to aide him only knew that his odd tests were somehow putting Luna and I under scrutiny, though none but him knew how until he came before court once more. He suggested meeting in private as to avoid his findings going on record but we declined. It was a series of little things with which he drew rather large conclusions from. Here is the record:
“The suns position on the horizon does not change with altitude. My plumbob with the longest twine possible did not move in the slightest throughout the day from sunrise to sunset.Things fall to the ground and the sun and moon are round. And on the subject of night, the number of apparent stars did not change from full moon to new moon.
The sun not changing with altitude suggests either the world is flat or the sun is too close to allow the curvature of the planet to be seen with changes in height. The sun and moon however appear round due to their spherical nature as the force pulling all things together still dictates and is seen through things falling to the ground and therefore this planet too is spherical. There is a minimum size a star can be and maintain fission and my plumbob did not get pulled towards the sun when perpendicular, at sunrise and sunset, despite how close the sun must be by previous tests. Naturally due to scaling the sun and moon must be quite close and therefore small to ignore the curvature of the planet.
And then there is the fact that the night is ignoring light pollution, and is frankly lacking in stars during the new moon. I have not removed my visor since I saw that insult to the cosmos' beauty. The only thing I can think of to explain all this is some sort of elaborate illusion set up to be a foundation from which a structure of power can be built. Now with all this out in the open, what is it about your fake sky that prevents me from seeing it?”
Now saying everything we have done for all that time was a lie was a lot, but on top of it insulting her night sky was too much for Luna. Such insults to royalty were unheard of at the time and Luna fired a beam of magic at him, which went through him as if he wasn't there. As you know every creature has a type of magic that is natural to them. He was known for saying there was no such thing as magic, that magic was just a scapegoat to fill the void of knowledge. Well his innate magic allowed him to not interact with magic much like gold and magnets. We finally had his answer, he could not see magic. When I tried to inform him of this new reason, the suns magic nature, he did not respond as I had hoped.
“If that was the case you would be violating the second law of thermodynamics by having a closed system that maintains chemical complexity. Clearly you cannot give up your inherited lie so I have no choice. I shall put it to the proper test of my kind. I shall seek to destroy it from every angle with everything I can and if it is indestructible then it must be true. However if I am right, and let's be honest we both know I am, then it shall be destroyed and abandoned.”
We found he is not immune to magic he must choose when to ignore it and we took the necessary steps to stop him. Rumors spread about how we silenced a creature with evidence against our power over the celestial bodies and ponies began to doubt us. Until one day a riot broke out over a historical lecture involving the balance of power of the three pony tribes before Equestria was founded, from the standpoint that he was right about the nature of the sun. The loyalists fought the academics. When the royal guard stepped in things escalated and it turned into an all out revolt between those with faith in us and those that had room to doubt us.
Doubt grows with knowledge, as such, his close ties to the intellectuals cost us many skilled workers, a great deal of whom were lost in trying to contain the chaos he caused. During the revolts a spirit grew in power until he took Equestria by storm and Discord’s reign began. All the while the seed of self-doubt he planted in Luna over her night festered until it became too much and she became Nightmare Moon. The country was nearly torn asunder in the fallout of his elaborate plan. He called himself Quid pro Nosco but we know him as Doubt.