The Mappa Mundi and the Imperial Departmento Cartigraphicae Map of the Milky Way

In the Warhammer 40k universe, the Departmento Cartigraphicae is the branch of the Adeptus Mechanicus that is tasked with mapping the eternal void of space as the Explorator fleets chart its depths. The map of the Milky Way that they have devised is similar to the Mappa Mundi and the Medieval concept of a map portrayed in Medieval scripts such as The Travels of Sir John Mandeville. Just as Jerusalem, the focal point of the Christian faith, is the center point of the Christian-centered maps of the Medieval era, so too is Holy Terra, formerly known as "Earth," the focal point for Imperial maps that chart the galaxy. Terra is the holiest and most cherished planet in the entire Milky Way Galaxy as it is not only the seat of Imperial power within the religiously fanatical Imperium of Man, but it is also the birthplace of Mankind, a race which is inherently holy and destined to rule all creation, and subsequently the Emperor of Mankind, the Eternal God of Mankind made flesh to lead Holy Humanity to its final victory. In addition, similarly to how the Mappa Mundi is divided into three sections, displaying the continents of Europe, Africa, and Asia, the map of the 40k universe is divided into five sectors, each being a distinct section of the Milky Way Galaxy. In the Mappa Mundi and in Mandeville's Travels there is the concept that the farther one travels from Europe and Jerusalem towards the edges of Africa and Asia, the more bizarre and stranger the world becomes. This same concept is also prevalent in the map of 40k as the farther one moves from Terra and the Segmentum Solar, the sector in which Terra resides, the more terrible and grim the galaxy becomes, with the exception of the Segmentum Pacificus, which resides on the farthest "West" part of the galactic map, farthest from the horrors of the galaxy, similar to Europe in Mundi. The Segmentum Obscurus and the Segmentum Tempestus are both farther to the "East" and farther from Terra, but still somewhat close, thus they both are fraught with enemies that the Imperium of Man is relatively familiar with such as the heretical forces of Chaos who's holy war with the Imperium is reminiscent of the Crusades and Jihads fought between Christians and Muslims. In addition to heretics against the Imperial truth, these sections of space are teeming with monstrous xenos races such as the hyper-violent and crude Orks or the hive-minded killing machines that are the Tyranids, and alongside them are tamer, but no less alien and no less threatening, xenos races such as the collectivist Tau or the ancient and immensely wise Eldar. In these sectors of space, human worlds are also home to various races of abhumans, subspecies of humans that were born from genetic mutation brought about by the living conditions they found themselves in on foreign planets. These abhumans are similar to the almost human monstrous races featured in the Mappa Mundi and in Mandeville's Travels. The ratlings, for example, bear resemblance to the troglodites portrayed on Medieval maps and in Medieval travel narratives as they are nearly human, yet they have grown much shorter than the average man and are agile and rat-like due to the tens of thousands of years they spent trapped underground in squalid conditions as the surface of their colony world was irradiated and toxic. Another abhuman race are the ogryn, violent, simple-minded, and extremely large, they resemble giants portrayed in Medieval texts. They came to be because their home colony was subject to extremely high gravity due to the planets incredibly dense core. Lastly, the Segmentum Ultima comprises the farthest "East" expanse of the galaxy and contains the galaxies most ancient and mysterious threats. Farthest from the Emperor's grace, the Segmentum Ultima is home to xenos races such as the Necrons, an army of undying, immortal machines bent on the eradication of all biological life, or the cold, calculating Rak'Gol, about which almost nothing is known aside from their periodic attacks on human ships and worlds, harvesting all sentient life and disappearing back into the void before any had the chance to respond to the distress call. All in all, the maps of 40k and the Christian Medieval era bear many similarities to each other in the way they are designed and in the monstrous beasts that inhabit their fringes.

Space Marines and the Ideal Medieval Hero

The Space Marines from the tabletop game, video game, and book series Warhammer 40K display many characters that medieval heroes tend to hold, especially in reference to those depicted in The History of the Kings of Britain. Just as their medieval counter-parts fight to defend their people and secure land and resources for the citizens of their respective nations, the Space Marines are first and foremost the staunch protectors of the Imperium of Man, fighting bravely against foreign hordes and securing a place for the human race in the vast expanse of the Milky Way Galaxy. Just as Brutus was for the Trojans, or Arthur for the Britons, the Space Marines are renowned amongst the citizens of the Imperium as extremely formidable warriors, gifted with the blood of the Emperor's sons, they are more than man and are the finest soldiers the Imperium has to offer. Comparative to Christian heroes such as Arthur or of later medieval texts, the Space Marines are credited for their religious zeal for the one true faith, which is in this case, the Imperial Truth. Their religious fervor and reverence for the one true God is a detail that makes them more heroic, at least in accordance with medieval values. In addition, just as medieval heroes are to practice the code of chivalry, the Space Marines adhere to a chivalrous code of sorts, known as the Codex Astartes, which serves as a book of guidelines as to how warfare should be properly and honorably conducted. Similarly, in a world fraught with disloyalty and treachery, loyalty in highly valued amongst medieval characters as well as in 40K. Just as characters in medieval literature are prone to become turncoats for the sake of personal gain, Space Marines of weaker will power are prone to renouncing their faith in the Emperor and turning to serve the Ruinous Gods of Chaos. Thus, unwavering loyalty and unquestioning obedience for righteous authority are highly applauded features in both Space Marines and medieval heroes. In addition to being similar to the idealized attributes of medieval heroes, Space Marines also bear semblance to the more brutal and not-so-heroic attributes of those same heroes. Just as Brutus arrives on foreign shores and slaughters many on his journey to Isles of Britain, or Arthur waging war on the pagan Picts or Saxons, the Space Marines purge entire populations in the name of the Emperor and are revered as heroes for it. Whether it be civilian alien populations or human populations in revolt or in heresy against the Imperial Truth, the Space Marines have lead countless thousands of genocides throughout the millennia in order to maintain the tenuous peace that binds the Imperium together. However despite such atrocities the Space Marines are venerated as the exalted heroes of Mankind, just as medieval heroes who commit similar deeds are still held in heroic regards by the people whom they rule. All in all, the Space Marines of the Warhammer 40K universe, and the knights and heroes of medieval literature are all formidable warriors, ferociously loyal, religiously zealous, and willing to commit atrocities in the name of the greater good.

The Emperor of Mankind and King Arthur

     The Emperor of Mankind from the tabletop game, video game, and book series Warhammer 40K shares many key features with the character of legend, Arthur, King of the Britons. While the only visual similarity is that both men seem to have an affinity for gold when it comes to their choice of armor, both do similar things and serve similar functions in their respective
stories. Just as King Arthur united Britain against the Saxon invaders and ended that crisis, the Emperor unified mankind in its darkest hour, an era in which the long standing Human Empire collapsed, leaving millions of colonized worlds and trillions of people defenseless against endless hordes of alien invaders, starvation as there are no longer trade fleets, or at the mercy of anarchy and civil strife. Both men saved their respective nations in their time of need.    
     Even comparable to King Arthur's Knights of the Round Table, the Emperor of Man had twenty sons known as Primarchs, who, gifted with the Emperor's superhuman
genetic legacy, served as the champions and generals of the armies of the Emperor's Holy Imperium. And speaking of Holy Imperiums, both men are often referred to in a religious context, where the Emperor is referred to as a literal God-Emperor of Mankind and that humanity itself is inherently holy, even going so far as to see the Emperor's sons revered as literal angels by the common people of the Imperium. While Arthur is in no way held to such an extreme degree of reverence, he is still regarded as a great exemplar of a good Christian king, favored by God, and upholding the principles of Christendom. In addition, both men are often depicted with halos about their heads in various illuminations and iconography of them.
      The two men even share similar figures in their individual retinues of followers. Where Arthur has his magician, Merlin, capable of seeing into and predicting the future, the Emperor has a man by the name of Malcador the Sigillite, who served as the Emperor's chief assistant, but also possessed the ability of foresight into the future as well as the ability to telepathically communicate with others thousands of light years away. Both are also depicted similarly, as a cloaked, wise, and mysterious wizard of sorts.
     Ultimately, both Arthur and the Emperor meet similar fates. Where Arthur is grievously wounded in battle by the traitor, Mordred, the Emperor is mortally wounded by his first and favored son Horus during the final battle of a long and bloody civil war known as the Horus Heresy. Similarly to how Arthur was brought to the Isle of Avalon to live out the rest of his days wounded, the Emperor was interred upon a machine known as the Golden Throne, a machine that maintains the Emperor's "soul" as his body slowly decays. Lastly, both men are fabled to return in the future to serve their nations. Where legend states that Arthur will return to lead Britain once again, the citizens of the Imperium await the return of their eternal God-Emperor, so that he may lead Mankind to a final victory against any that would seek to harm it.