Elysiamaetrixus is the first ever forged longsword, making it part of the Caellian arsenal. Like all weapons of its divine kind, it was forged by Caellus during the Era of the Moon. This particular weapon was used to knight The Six when they swore the III. The Elysian Promise.
It's current whereabouts are unknown, as it was never seen or mentioned after this event again.
Like all weapons in the Caellian Arsenal, the weapon is engraved with "Elysium. Decorous. Aeternus". Whenever wielded by one of the Primunati, it will shine silver in the moonlight; whenever it is wielded by one of the Secunati, it will shine gold in the sunlight. During an Eclipse, the weapon always shines, but still in accordance with its wielder.
The essence of these weapons cannot be extracted. Neither can the weapon be broken, with a single exception: by another weapon of the same nature, bearing its opposite light.