The God of Darkness made the Grimm before he collaborated with his brother to make men. But in the time before men, before he discarded one creation for another, the world was theirs'. Before the world was reduced to a remnant, they grew old and fat and ruled over vast swathes. Humans have always known of Grimm, but haven't always known what they were: mistaking them for animals or forces of nature, or even gods themselves, were they so massive. They were the shadows at the edges of the world, and they did not care for the new chosen inhabitants robbing the kings of their thrones.
There are many stories of the Grimm of the past: of creatures so massive they appeared like moving mountains or had wings to block the sun, or of Grimm so old and wizened they spoke in a tongue men understood. Each region has its stories: from the king of a lost country reduced to a shadow wandering the deserts of Vacuo, to the whispers of a 'queen' the Grimm now answer to. Most of these stories were once accepted as history, but most have been dismissed as nothing more than local legend.
There is one myth that persists in Atlas, because it has always interested the greedy and ambitious: a tale of a man whose monstrous lust for gold turned him into a Grimm.
His name is lost to history, but this was a common practice at the time. He was stricken from all records because he committed the most terrible crime of all: he killed his own kin to hoard the wealth to himself.
The exact story has been retold so many times the exact truth has been lost. In some versions the treasure belonged to the father of these two men, in others they stumbled upon it while working together as miners. But each story has the same ending- one brother murdered the other and hoarded a pile of gold as vast and deep as a lake. He called it a barrow; a burial mound for his departed brother, but it became his tomb as well, for he could not leave the gold for even a moment, he was so consumed with his greed.
It doesn't take much convincing for powerful men of Atlas (and before, Mantle) that there are vast riches beneath the rock and snow; they've spent centuries digging deeper down in pursuit of that wealth. It doesn't seem implausible to them the treasure awaiting them is so immense that someone would be tempted to commit a terrible crime to possess it.
What they do not believe is the common ending of the story. They dismiss it as some added morality play; some claim to scare children and dissuade them from chasing after treasure. But so many versions of the story exist with the same ending it becomes impossible to dismiss entirely, no matter how hard it is to comprehend.
Greed is a negative emotion, after all. It too would summon Grimm. What they refuse to believe, however...
...is that any man's greed would be great enough to become a Grimm.
And yet, that is what became of the brother, resting and bathing in his golden glow. Either as punishment by the gods for his crime or his greed becoming so great he willingly traded his soul to sate it, the man became a Grimm.
The next time the treasure was found was when a hero of Atlesian myth sought a magical ring buried amidst the pile of riches. He had no quarrel with the monster guarding the hoard, and wished but for the smallest trinket. But the man's greed would not allow him to part with even a kernel.
The hero announced his intent. "I wish only the ring, so I might use it for the sake of another. I have no claim on your riches, nor seek to offend you in your house."
In some versions of the tale the man-turned-Grimm lost his power of speech. In others (the ones children prefer) he answered in ruthless denial: "Your armor and sword shall be added to my riches and your body laid rest upon my barrow. You think you can come into my house and demand my favor? You are but my possession already. You will forever adorn my house as warning and trophy."
The hero pleaded with his host not to fight. He was seeking to save one he loved, not to see further blood shed in the beast's house. One brother died already, and there was no need to kill the other.
And the beast gave answer: "Upon my barrow, I decide what remains. All that enters my house is mine to have and hold; I am king under the Mantle!"
They fought. The hero put aside his compassion and slew the Grimm. But true to his word, he left the hoard; he wanted only a tiny ring to use its unique magic and save the woman he loved. He left his sword embedded in the beast's torso, through its black heart, pinning it atop the hoard it had so coveted.
Men of Atlas believe there is gold beneath the surface of their kingdom. They believe if any struggle was fought over it, they may well find skeletons and a rusted sword floating atop a lake of gold.
They do not expect to find a Grimm larger than any other; fueled by centuries of burning, ceaseless greed. They do not expect a rusted hunk of metal holds it between life and death and ensures it remains sealed away. They do not believe any Grimm -even Grimm once men- proclaim themselves kings.
They are wrong.