When the gods began their war against their creators, the Primordials recognized that they would need potent weapons to defeat their upstart offspring. Using a precursor to what is now known as soulforging, the Primordials took one of their lesser souls – what today would be termed a demon of the second circle – and melted it till it ran liquid. They forged it together with a mighty sword of obsidian and a material now lost, which became brass in the banishment of the Yozis to Malfeas. This, however, was merely a powerful weapon – not nearly puissant enough for the destruction of many Exalted and gods. The final ingredient was the stuff of betrayal itself – the essence of the gods’ treachery against their creators. Alloying together this betrayal with the demon-stuff and mighty sword, they forged the Blade that Walks in the Night and Devours Oaths. Not entirely demon, or weapon, it struck not only at material armor, but at the bonds of brotherhood and allegiance themselves. It manifested then as a man-shaped shadow with brass bangles about its wrists and neck, with a huge brass-and-obsidian blade gripped in its inky claws.
The Unfailingly Righteous Brotherhood first encountered the Blade that Marches in the Night in the far West, where they were aiding a pack of Lunar Exalted in destroying the Behemoth called Khanakakana, a twelve-limbed thing of scales and claws, which possessed no eyes and yet saw with perfect clarity; had no mouth, yet consumed all it found. Lintha warriors rode its mile-long back, and it was beloved of Kimberry, the Sea that Marched Against the Flame. On the island called Khana-tak, thirty Dragon-Blooded, six Lunar Exalted, and five Chosen of the Sun did battle with Khanakakana, and slew it. As it fell, Kimberry begged her brethren to unleash the newly-forged Blade. They agreed that it was time to deploy the weapon, and sent it out into the world. At the spot where Khanakakana had been slain, the ground bubbled, almost boiled, then erupted into the form of the Primordial-forged weapon.
Within minutes, all six Lunar Exalted and twelve of the Dragon-Blooded warriors who had accompanied the Solars were slain by the Blade’s mighty sword. It left the Solars covered in their companions’ blood, laughing as it ran across the waves to the shores of the West, where it cut away the allegiance of an entire city and turned it into a hateful swarm of man-shaped beasts that attack anything they see. Another city, Amana-on-the-waves, was subjected to the Blade’s work and its inhabitants found themselves still dedicated to their city, but unable to find much love for any of their fellow humans. The effect was a city packed with people who were deeply suspicious of each other, tolerating one another’s existence only because no one person could keep the city maintained alone.
The Unfailingly Righteous Brotherhood pursued the Blade across the West, always one step behind it. Twice, they were forced to destroy Terrestrial Exalted whose dedication to the Elemental Dragons had been sliced off by the Blade’s power. Nakaya and her circle caught up to the Blade just as it was cutting away the oath between two newlyweds. As the couple gazed at each other with newfound apathy, the Chosen of the Sun fell upon the Primordial weapon with battle-cries and ringing swords.
The battle was hard-fought. Only mighty spells and the Essence-channeling battle-songs of Noontime Glory kept the thing from devouring the Solars’ dedication to the Unconquered Sun. The warrior Taka Sings at the Dawn was the first to fall, skewered with the mighty obsidian blade even as he buried his orichalcum battleaxe in his enemy’s chest. Next was the Night caste Fu-na-ayala, who died with tears in her eyes for her Lunar consort, who had been among the six slain during the Blade’s first appearance. Their wartime romance had been one of the first of many Lunar-Solar loves to come in the First Age. The diplomat-sorcerer called Death Changes Nothing was decapitated with a spell on his lips, and the Twilight caste magic-worker Siuli destroyed himself to channel a mighty blast of Solar power, a beam of pure Essence that ripped off the Blade’s left arm. Nakaya fought on, and on the fifth day of the battle, a lucky blow struck deep into the essence of her enemy and destroyed it.
The Unconquered Sun called Nakaya before him and, before the assembled armies of the gods, spoke her praises for the destruction of the Blade that Walks in the Night and Devours Oaths. When her patron asked Nakaya what reward she would ask for the deed, she declined. “I deserve no praise, my lord. My fallen brothers’ glory is as lions’,” she said. “Mine is that of a mouse.” In response, Unconquered Sun laughed, and with a grin said, “Then I have need of more such mice in my armies” He handed Nakaya a wooden box inlaid with ivory and orichalcum, with a small carved image of a mouse on each side. Noontime Glory opened it, and beheld four small mice, each bearing the mark of the Sun on its back. Thus were created the Mice of the Sun. In time, Nakaya and her reincarnations became known as the Mouse – at first a joke, later a title of respect.
(To add later: The reforging of the Blade that Walks in the Night and Devours Oaths with the treachery of the Dragon-Blooded and Sidereals against the Solar Exalted, and its second destruction on the eve of the Usurpation by Telen the Bloody Mouse and five loyal Terrestrials, and the possibility of a third creation alloyed with the betrayal of the Deathlords. The second forging was ivory-white with brass armor, and the form of a third casting is, of course, unknown...)