Littlepip, primarch of the Ultramares.
 
After being sent the Black Book by Rarity on accident, Princess Celestia instructed Starswirl the Bearded to research everything he could about Zebra Magic and their “Star-Gods”. As he continued his research in secret, not wanting the public to know that Equestria’s greatest sorcerer was investigating Zebra Magic, Starswirl discovered many terrifying truths, however, before he could inform the Princesses of his discoveries, the Megaspells were launched. Starswirl survived the Pink Cloud due to his magical expertise and recent discoveries in the realm of dark magic, however, he wasn’t able to prevent himself from being transformed into a ghoul.
 
Starswirl explored the wasteland, trying to find what became of Celestia, as he could feel that her soul was still present in the world. After centuries of searching, wandering the land, tinkering with new weapons, armours, and genetic enhancements in his spare time, Starswirl managed to find his princess, her soul trapped within a machine. Starswirl freed Celestia’s soul from the machine and kept it safely bound with a magical ward inside a talisman, then Starswirl gathered ingredients, including the numerous corpses of ponies of all species for the necessary biological material, Celestia’s bones for DNA samples, and several barrels of IMP. Using these ingredients, Starswirl created a new body for Celestia, stronger and more magically gifted, and proceeded to deliver it to Maripony, as a “gift” for the goddess, he offered to bind Trixie’s soul to the new body, provided he can prepare the ritual to do so… The goddess agreed, and Starswirl prepared the spell when he began, he released the soul of Celestia into the goddess’s gestalt mind, she quickly overridden Trixie’s mind, and gained full control due to her soul’s superior will, then the ritual was completed with the newly reborn Celestia having her soul bound to her new body.
 
The Empress, Celestia, now possessed control over the Alicorns, however, she freed them from their psychic hive-mind. Then, upon seeing the destruction wrought on Equestria for herself up-close, she decided that she must end it, and rebuild her kingdom, and Starswirl was quick to inform Celestia about the danger the Star-Gods pose, Starswirl then took Celestia and her alicorns back to his laboratory in the Crystal Mountains, where Starswirl practised his new genetic modifications on the alicorns, those alicorns who survived the process were doubled in size, almost reaching as high as Celestia’s new body, and were given a host of biological enhancements courtesy of the modified IMP that Starswirl had developed.
 
These new alicorns were dubbed “Custodians” and were given power armour to better protect their new Empress. Celestia then went out to rebuild her kingdom and oppose the Star-Gods. Most wastelanders simply surrendered upon seeing Celestia herself, the raiders and slavers were, for the most part, purged, and those who accepted the offer were given the honour of being genetically modified themselves, becoming Thunder Warriors. The Reunification Wars spread out from Maripony, Manehattan was the first city to be occupied, along with all its settlements, Tenpony, Friendship City, Arbu, and the Manehattan contingent of Steel Rangers, all either surrendering or being forcibly absorbed into the new Celestial Imperium.
 
From Manehattan, the reunification spread southward to Fillydelphia, where a majority of Red-Eye’s forces would be crushed in the ensuing battle against the Thunder Warriors and Custodians. With a powerful industrial capital, Celestia could bolster her forces with armoured vehicles, Mark II power armour, Mark I terminator armour, and the new Phobos Pattern Boltguns. With all this and another thousand new Thunder Warriors, the Reunification was able to spread further south and west, to Canterlot, Ponyville, Las Pegasus, Salt-Cube City, and Hoofington.
 
Littlepip was one of the few Primarchs to seek out the Empress during the Reunification. Not long after the integration of Manehattan, right before the scouring of Fillydelphia, Littlepip ventured to Tenpony Tower following her escape from Fillydelphia and Red Eye’s techno-barbarian horde. There she encountered the Empress and swore her fealty almost instantly. After joining up with the Empress’s forces, she was sent to work as an advisor for the invasion of Fillydelphia, she would then go on to serve as a strategic advisor to the Thunder Warriors and was the pony to first suggest recruiting an army of normal ponies to serve as support to the Thunder Warriors. She continued using her tactical genius to great effect during the pacification of the Enclave, and along with the primarchs of the IX and X legions, she convinced Celestia to grant the Enclave a measure of independence in the new Imperium.
 
Littlepip would be selected XIIIth in line during Project Primarch. Her legion of Space Marines would be named the “Ultramares” and would bear the symbol of a horned horseshoe. Her commanders would include the Captian of the Ist company, Murky, who would be mortally wounded during the battle for Colth… His life would be saved by the intervention of the Primarch herself, who would take the dying marine and give him over to the Archmagos Biologis Lambent, and would later be known as the first of the Primaris Marines. Littlepip has recently been awoken from stasis following the 13th Black Crusade.
 
Notice: To me “intellectual property” is an unjustly authoritative law created by self-centered businessmen for the purpose of gaining wealth and preventing the “filthy peasants” from touching their creations, the art I create is meant for everyone, not just myself, thus feel free to use my work however you see fit as long as you aren’t an asshole about it and give me some amount of credit.