The Crimson.
Legends had it that somewhere deep within the bloodied soil laid the carcass of a great evil, an existence so vile that not even death could stop its rotting flesh from subsuming and corrupting everything it touched. It was remains of the last spawn of Foreigners - a species of unfathomable abominations hailing from the End, the void where everything had, was or would ever be was fated toward. And these creatures emerged from the edge of the End like Evil itself coalesced into existence crawling out of the abyss. They consumed planets and razed star systems with abandon as if it was their sole purpose of existence. Reality itself quaked in trepidation before their rampage, and only the combined power of the Realm Keepers – the guardians of life across the multiverse, tasked with looking over their bestowed universe - could oppose them in their mindless pursuit of cosmic annihilation. Their crusade against the utterly alien beings shook the border of worlds as if there is no longer the concept of space or time, life or death, only endless battles.
But one couldn't kill that which was never alive to begin with, and so each Foreigner slain gave ways to another rising from its corpse, devouring its fallen kin before turning its maws to the next meal. And when it seemed as if the Realm Keepers had started to push the Foreigners back, they started turning on each other in the midst of battle, feasting on each other's flesh to evolve. Stronger. Faster. More intelligent. Until there remained the last one, yet also the strongest and wisest, one nothing sort of the Great Creator could hope to win against. And the guardians fell to both the Foreigner and the despair in their heart, in a desperate gamble to save the multiverse, one Realm Keeper had made their ultimate sacrifice. For every Keeper held their realm close like their most sacred treasure bestowed upon them by the Great Creator, their decision was paramount to denying their strongest calling, their purpose for existence. Terra tore open the fabric of their universe and sealed the Last Foreigner inside, using their Ascended Soul to forever isolated it from everything, never to emerge again.
The gamble worked. Terra has paid their existence as a price to forge the ultimate concept of this miserable world. This universe shall forever be closed and isolated from everything, existing on another plane and fated to burn out without the connection to the soul circulation of Life and Death. Alone with a thousand voices urging for destruction, the Foreigner raged for millennia. A malevolent being with unimaginable power chained inside this universe and only a tiny world to feast its desire upon.
And then it stopped. The Foreigner learned to dominate the mind of every kins' minds, becoming a unique being. A Beast with a Name, an Ego. A Beast that in its mindless lashings had learned Deception, Cruelty, Sadism and every concept whose lesser versions existed within us as negative emotions. No longer shackled by the thoughts of destruction, it craved for the Joy of instilling Fear, Sadness and sweet Despair upon lesser beings. With boundless power on its metaphorical fingertips, the Beast rejected the dispersion of souls upon death, effectively creating its own version of Life and Death, so that these lesser souls will be forever immortal for it to torment, from this life unto the next. It planted the seeds of civilizations, giving them the privilege of wisdom beyond mere animals. They were given strength, hope and faith, and it basked in their prayers as their God, only to slowly torture the naïve zealots into extinctions as their fragile minds cracked with the belated realization that the benevolent Gods they worship and revered was the ultimate Evil all along. Eras after Eras, it crafted more elaborate ploys, schemed more sophisticated plots like a gourmet contemplating what delicacy they shall make of the next ingredient. It toyed with us, whispering tales of Heroes and Demon Lords into our dreams, setting the stages and watching the shows unfolded. Sometimes a General of the Demon King, some times the vassals of the prophesied heroes, some times just a silent observer from above, it relished in the role of the string-puller, the Puppeteer, the Silent Observer. And foolish lesser beings, in their wistful observation of the stars, thinking about the unreachable celestial bodies watching them like a thousand eyes of Gods, had named it after the greatest star of the night – The Moonlord.
The universe imbued with the essence of Terra wept in despair until it found something the Beast could not detect in time - a true Hero. Informed of the hero in their slumber, what force remained of Terra's vassals whisked them away to the edge of the world, training them, making them stronger, hopefully for a final confrontation with the Moonlord. Their humanity fractured in the process, yet held together in a unique being - a vessel of Terra mind and power, with the heart of a human. Ancient epics had it that the Moonlord had been defeated at the end by the chosen one of Terra, bestowed with a legendary weapon capable of slaying gods and deities alike – The Terra Blade. The hero had plunged the sword into the Beast's core, sealing themselves and the Beast's immortal consciousness and battling with it till the end of time. The hero's sacrifice had put an end to the once powerful Foreigner, scattering its soul to the world, becoming wandering mass of energy, never going away, but forever dormant without its consciousness to govern. The largest remains of the beast fell to the end of the world, corrupting and converting everything it touched until a piece of the world became an ever-spreading, writhing realm of blood and gore. The Living World of Death. The Land With A Thousand Eyes. The Crimson. Or so the epics led people to believe.
Yet human simply could not take that as the end of the story. Perhaps in a idealized sense of justice, or a thirst for revenge, they gathered. Warriors of mighty blades, mages of thousand spells, rangers of thousand miles shots, all united under an organization to eradicate the great Evil from this land once and for all. They ordered troops on expeditions to seal the spread of the Crimson with anchoring altars. The Holy Crusade, they called it. One hundred and fifteen years to push back the infection, facing stronger and stronger monsters as they approached the continent where the corpse of the Moonlord laid. Starting as a organization of mercenary with noble purpose, they had become the most prominent military force of the world. Going through strict and rigorous training to achieve inhuman strength and power, they were the elites of the elites, the Hope of Humanity, the Terrarian. Their exploits against the demons and monsters of the Crimson instilled a thirst for glory and greatness in generations of youth, and enlisting as a recruited member for the Terrarian was an honor beyond any other riches or fame, sometime perceived as the rite of passage to become a full-fledged adult. Iron were the acting militia of countries, keeping the job of exterminating stray monsters and ready to be draft into reinforcement for any expedition, with Silver being full-time soldiers and mages. Gold were commanders of local Terrarian Guild, situated near the edge of the border to guard the containment altars. Platinum were the equivalent of great generals and one-man armies of their own right, capable of fighting with the strength of a hundred men, and Diamonds were national figures with inhuman strength and protections and divine blessings from agents of Terra, the like of which there had only ever existed a few through out the hundred year history of Terrarian, truly the epitomes of human's achievements.
Even then there was still a division that stood above all. One that managed its own recruitment and training, rumored to be the institution that nurtured every Diamond ranked Terrarian ever existed. They were the masters of arms and magic, said to have undergone training that surpass every limits of human body and mind. They were the Alchemy Knight.