When humans opened a gate to the abyss and took a look, it gazed back, at first humans thought they could conquer this realm, be its new master, just like they have done on several other planet, what they failed to realize was that they were dealing with a whole new beast entirely,
They thought with their advanced science they could conquer and rule over this beast, not realizing that what they thought to be the rulers of this planet, the 'ghoul beast' was nothing but pets the real masters the ghouls were a whole different story, they appeared as humans but they were entirely different, they were beast in the body of men, strength, speed it was like nothing humanity could ever imagine, they could out run bullets, tear through steel, as if it were paper, humanity was forced to flee from the gate.
Closing the gate they thought that it was all over, but they were wrong it was far from over, humanity thought they were more physically stronger than us, but we were wrong they were not only physically stronger than us, but more technologically advanced, were humanity made our technology efficient and aesthetically pleasing, theirs was crude and efficient, like they wore chainmail armor, we wore power suits, but they had something humans never accounted for 'Hex tech' it was carved using a mineral found in the body of ghoul beast, which then melted and used to draw the hex runes on the armor, swords,, so basicly everything they use.
So closing the gate didn't help, because humanity fought the ghoul beast, they were tracking our dimensional coordinate, so when they decided to reveal them selves they already had our coordinate pinpointed and come to our universe when ever they please.
After closing the gate, humanity had a sense of peace for while, when suddenly earth sky cracked open, and with flying ghoul beast flooding out of it, it was chaos and humanity was not prepared for it, and from the depths of the crack in the sky, they war ships, billions of them, it was the end, fear was prevalent through out the entirety of earth,
But like always humanity chose to fight for survival, we brought out our burning battle spirit, our power suit, guns, war ships, nuclear war heads, hid in the deepest darkest bunker on earth, ran research on how to survive, we did everything we could to survive but,
We stood no chance of survival, humanity was on the brink of falling, until suddenly, there was a ray of light in the darkness, a glimpse of light in the darkness, a chance of survival had appeared, a scientist discovered that the energy nucleus located in the heart of the ghoul beast could be harness, and when used together with the flesh of the ghoul beast, could be use to create a kind of synthetic suit, that could boost speed, strength, agility, durability, in fact it could make someone super human, with the only downside being it took a toll on vitality, and with the suit in hand, humanity killed it first ever ghoul, which caused a celebration through out humanity, with this humanity had regained hope, with some naive ones they even thinking that they could some how win the war,
But the higher ups of humanity knew they had no chance of wining the war, so instead they gathered as much humans as they could, the rest were given the ghoul beast synthetic suit (GBS suit for short) as a distraction for the rest of humanities escape.
The bunker which humanity was hiding out in could be used as a space ship for escaping the planet in time of emergency, it been equipped with space jump, light speed with a fixed coordinate Mars,
It took approximately five years for humanity to make preparation for their plan, of cause only the higher ups of humanity knew the plan the rest thought that it was war preparations,
Soldiers were deployed to the front lines, wearing GBS suits, fighting fiercely with the ghouls and when the war was at its climax, the leaders of humanity, executed their plan, lunching the bunker into space, and making their escape to mars, the soldiers left behind lost hope and surrendered awaiting their death, but what awaited them was a contract instead, and this was when the first generation of half ghoul was born.
The escaped humanity blew up the earth core in hopes of killing the ghoul once and for all, but they had grossly underestimated the ghouls and their technology,
The explosion of the earth core did happen, but with the technology of the ghoul they were able to not only nullify the explosion, but also using the explosion to further strengthen the earth core, but they didn't give chase, to them humanity was already a cornered rat.
And with the successful escape of humanity to mars, they saw a period of peace and prosperity, it wasn't until ten years later that first sign of movement of ghouls were found,
Humanity faced the result of its own treachery, because what came for them wasn't the ghouls that drove them to despair, but the soldiers they left behind, but something was wrong, they looked the same as how they left, it was as if they didn't age a single moment from when they where left.
The half ghouls, or how they would later be called in the future 'despair soldiers' lead billions of ghoul beast, and with that humanity faced its third war with the ghouls.
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Summary of all the war between Humanity and the ghouls, The first which will be called 'Look into the abyss' occurred when humanity had only just opened the portal to the abyss plane, the home world of the ghoul and deciding to conquer it.
The second war 'Gazed at by the abyss' happened after the defeat of humans in the abyss plane, and their subsequent retreat, leading to the invasion of the abyss.
The third war 'price of treachery'