Blanks are a species of cloned pony that seems closer to docile animals than actual ponies. They are created fully grown and lack the higher intelligence found in all the other pony species. They appear in Fallout: Equestria - Project Horizons.
Blanks are created from a special arcane machine known as a Tree of Life, first encountered in the halls under Hippocratic Research. When Flux is pumped into the tree, a number of bulbs on it's 'branches' will begin to grown and swell into large (usually white) sacs, which eventually split open to reveal a newly created Blank.
Standard Blanks are albino, their bodies utterly lacking any pigmentation. Due to their near empty minds, they spend most of their time simply wandering around their surroundings, seemingly in search of food (however those that do not happen across food will simply let themselves die of starvation). They lack the intelligence to perform even the simplest of tasks (such as opening food wrappers) and most will simply die if they aren't looked after. All of these Blanks are earth ponies, and none of them have ever developed a Cutie mark. They seem to act closer to pets and docile farm animals. Brass would feed Blanks to her Manticore pets and Blanks that came into contact with raw Flux, would bloat up and become 'fatties'. The fatties can be quite dangerous, especially if they are under the effects of rage though are otherwise they are as harmless as other Blanks and continue to meander around their surroundings.
Cloned Blanks are created when another Pony's D.N.A. sample is injected into one of the branches of the Tree of Life; when this happens, the bulb will take on the color of the target Pony's coat, and soon grown and split open to reveal a near-perfect clone of the original. Despite being physically identical, the Cloned Blank still has no mind of its own, is sterile due to an inability to produce the necessary hormones to support a fetus and lacks the original pony's cutiemark.
Interestingly, while Flux mutates Blanks into fatties, taint (I.M.P) has been shown to have a healing effect on Blanks, making them feel energized - this may also explain their apparent resistance to Enervation. It is also speculated that they have longer life-spans than naturally born ponies, though the exact average length is currently unknown.
During the war
Blanks were first created as part of Project Chimera as a means of creating disposable test subjects, though soon saw use as organ donors, being created so that organs could be farmed and harvested from their bodies (this was due to the Ministry of Peace's desperate need for organ donors at the time). Following the shutdown of all secret O.I.A. projects by Princess Luna in the month leading up to the last day, the Tree of Life was kept active both due to it's usefulness to the M.O.P. and to act as a drain on the source of Flux.
After the war
Blanks continued to be manufactured two centuries after the war, the machine creating them seemingly running automatically. By the time Blackjack and her companions reached the Hippocratic Research Laboratories, the halls were filled with Blanks; some being converted into fatties for use as shock troops against the attacking robotic forces of the Hoofington Core, while others were simply being used as a food source or for target practice. Sanguine used the Tree of Life to make himself and his family four cloned Blanks for megaspell fusion, and two blanks for Blackjack's skin graft and Scotch Tape's organ replacement operation.
The Blanks and the method of Blanks was thought lost when Blackjack freed Discord and destroyed the Project Chimera laboratories, preventing them from being used by Red Eye or other Wasteland powers. It was later discovered however that a Thunderhead Enclave science team found a small scale version of a Tree of Life (apparently a sapling or trimming), suggesting more may be in existence; this "Tree of Life" is currently too small to create Blanks ,however.
After learning of Discord's alias of 'Coyotl' from Shujaa, Blackjack correctly deduced that the mysterious Brood of Coyotl are in fact Project Chimera Blanks augmented with cybernetics from Project Steelpony. These Zebra appear to be cloned Blanks, many of them zony unicorn mares, granting the brood a large force of combat spellcasters.
After encountering Cognitum and being forced out of her birth body, Blackjack's mind and soul was transferred to a Blank clone of her original body (created during her siege on Project Chimera) using knowledge and spells, in part, from Project Eternity. This successfully transferred her consciousness, as well as her cutie-mark.
After learning of Professor Zodiac's treason, a number of Trees of Life are now suspected to be operating in the old Four-Stars bunkers around Hoofington, explaining the massive numbers of Brood emerging from these facilities.
Boo - She is a notable Blank who has displayed above-average intelligence for a blank, able to detect danger and hide quickly. She also operated a mouth operated pistol in an attempt to assist Blackjack, although it seems that it was accidental. Blackjack rescues her from the Project Chimera labs, as they were pursued by an Ultra Sentinel. The idea that Boo is a "real pony" or has a soul is a matter of debate within the team.
Blackjack - During the attack on Project Chimera, Blackjack makes a deal with Sanguine to unlock Project Chimera in exchange for a blank of herself and Scotch Tape to replace damaged flesh and organs respectively. It is assumed these blanks died from their surgery and the self-destruction of the facility, however it is much later revealed that the robotic forces of Cognitum captured the Blackjack blank (along with a now feral Sanguine), believing it may come in handy at a later time.
After Blackjack is abducted by Cognitum, the machine assumes control of her body and transfers her mind and soul magically to the Blank clone, essentially giving Blackjack her pre-wasteland body back.
The Brood of Coyotl - It is revealed that the cybernetic forces of the Zebra remnant are in fact Zebra Blanks created by Project Chimera and augmented by Project Steel Pony. Shujaa clarifies that this is evidenced by their name; Coyotl is an old Zebra name for Discord, who's blood (flux) is a key component in creating Blanks. It appears that there are currently three Trees of life being used to manufacture Brood, supposedly in the old 4-stars bunkers.
It must also be noted that Psychoshy, while born naturally, underwent a Project Chimera Fusion Megaspell with a Pegasus Blank to stabilize her after her premature birth. Whether this fusion has imparted any of the inherent traits of Blanks, in a manner similar to the other Fusion test subjects, is currently unknown.