Executor

Executor was an alternate-world incarnation of the Scarlet Devil Mansion, a former Rainbow Factory and Anathemite.

Appearance
In his post-Factory form, Executor appeared as a mechanical winged unicorn with a rainbow mane and tail and the Rainbow Factory's logo for a cutie mark. For his role as the "High Lord Executor", his creator Arachnos made a few cosmetic modifications to him, turning one of his eyes bloodred and darkening and inverting the color of his mane. He also donned a tattered cape and a spiked crown.

History
Executor was originally an SDM until he was abducted by the Rainbow Factory Corp. and converted into a Rainbow Factory, of the type that utilizes live ponies as rainbow fuel. He operated with no notable incidents until Arachna warned him and his associates that his universe's version of Hellgate can destroy the entire universe by calling upon the power of Anathemus. Although such a scenario had indeed happened in one version of Equestria (leading to Arachna's fear), it had been a one-time fluke brought about by very specific circumstances. Nevertheless Hellgate was not without noticing everyone's newfound fear of him and proceeded to ruthlessly exploit it, allowing him to do essentially as he pleased in Equestria.

When there was nothing left to destroy, Hellgate commanded this world's version of Arachnos to take them all to another Equestria where he could cause more destruction. This is how the Factory and its employees, along with Hellgate, arrived to a much more technologically advanced Equestria. Through the perspicacity of that world's version of the Factory, it was finally revealed that Hellgate did not really wield the power to summon Anathemus. The invading Hellgate was driven away, and the Hellgate of "Techquestria" (at that point the CEO of the local Factory) was destroyed by mistake in the crossfire.

The agents of the destroyed Equestria's Factory became agents of the "Techquestria" Factory instead. The body of the newly arrived Factory was scrapped and recycled, while his soul was transferred by the local Patchouli into a robot alicorn body created through the collaboration of the newly arrived Arachnos and the local Arachnos. This is when he became known as "Executor".

Following various other incidents in Techquestria, he was one of four people (along with his versions of Lynna and Arachnos, as well as the Techquestrian Arachnos) who went to explore a mysterious otherworldly portal, dropping them in a strange dimension which came to be nicknamed "Esherland". After getting stalked by Nihilius, the group subsequently came face to face with Anathemus and were seemingly consumed.

Instead, they actually ended up in yet another parallel Equestria at war with the Nihilius Clan. Unknown to them, they were now Anathemites, Nihility-made shadows of their former, erased selves. Because of their bodies reading as Nihility on his sensors, the local Factory was fearful and aggressive towards them, while the Clan now worshipped them as "Gifts of Anathemus" destined to purge the world. The four of them were taken into the Clan, but they did not know yet that they were indeed what the Clan thought them to be. At any moment they expected to be unmasked as imposters and disposed of.

In order to allow his friends to gain the local Factory's favor without becoming the Clan's outright enemies, Executor developed a plan that involved him becoming the leader of the Clan, while the other three defected to the Factory (the Clan would believe their purpose was to spy on the Factory). In order to keep his ruse secret and preserve his friends' relationship with the Factory, Executor got himself fully in character and became a terrifyingly effective Clan leader, orchestrating multiple attacks that ravaged major cities, including Canterlot. Over the course of his stay in the Clan, his Nihility powers Manifested and developed. He finally became truly infamous when he kidnapped and "killed" Princess Luna (though unbeknownst to all, he actually only reduced her to a Nihility construct, and collaborated with her occasionally until his death).

Executor and his friends were reunited when the three returned to the Clan in order to develop their powers, with the approval of the Factory. Executor half-heartedly helped them train, but throughout it all he was often hostile to them - because he was fully aware they would one day have to kill him to keep the ruse a secret, and did not want them to sympathize with him. Nevertheless, the four had to work together against the threat of the invading Nihilius. At this point, the Clan even made a truce with the Factory to destroy the unnatural abomination which they believed represented the "End of the Dream". After multiple confrontations, the Anathemites and the local Factory's agents finally destroyed Nihilius in a grueling battle which saw the Awakening of their true powers.

Immediately upon defeating Nihilius, Executor "banished" the three other Anathemites from his Clan, branding them as "traitors" and resuming his assault on Equestria - so that they would not be able to take mercy on him and blow their cover. After a few more attacks, the Anathemites were finally forced to put an end to him in the city of Canterlot. Upon death, he accessed an unknown realm wherein he is presumed to have found peace at last, though its details have not been revealed yet.

The Nihilius Clan never learned of his duplicity, and Executor continued to be a legendary hero and martyr to their eyes, even though the other Anathemites were reviled.

Personality and traits
Executor's personality is what you would expect of an SDM, but somewhat more somber due to what he went through. He has absolutely no empathy for almost anyone except those closest to him, but willing to do anything for the safety of those select few - in that sense, the three other Anathemites became his surrogate "residents" over the course of their adventures.

As a commander of the Nihilius Clan, he was severe (but usually not outright cruel) and often rude (as incarnations of SDM are prone to be) to his followers, but because of his effectiveness as a leader, he was still beloved by them and remembered fondly as their greatest hero.

Skills and abilities
As an Anathemite, Executor was able to warp reality to his whim effortlessly.

He was also a brilliant strategist, elaborating plans which took even the equivelently intelligent Factory by surprise. By combining this intelligence with his immense power, he was able to overcome even overwhelming odds (such as the opposition of three equally powerful Anathemites) to accomplish his goals.

Weapons and combat gear
As a Rainbow Factory, Executor wielded the standard weapons and defensive systems of one.

As a mechanical alicorn, he was outfitted with a system that allowed him to receive power remotely directly from the Arachnos Array, and an auxiliary electric rechargeable power battery for emergencies. He was equipped with high-end rainbow weaponry and defense systems for combat purposes. Wings and thrusters allowed him to fly.

Theme
As High Lord of the Clan, Executor has a specific leitmotif associated with him, The Incomplete Stone (A Capella) from NieR Gestalt and Replicant. In some occasions, a combat-focused variation of the song was used instead.

Trivia

 * Because of his theme song, Executor is sometimes associated with the popular Youtube video "The Driver" in jest. One notable joke goes that his full title is "High Lord Executor, Hand of Hate, Hand of Salvation, Herald of Anathemus; His Great Gift to the World, who drives a tow truck".