Seniorious is a Dug weapon/Kaliyon that's currently owned by the Orlandri General Trading Company.
It is the strongest Dug Weapon/Kaliyon known to exist. Due to this the sword is extremely picky. Seniorious not only requires its wielders to be incredibly talented but also for them to have a tragic background of some sort.
The special ability of Seniorious is: the power to kill anything and everything. This ability accepts no exceptions. Only known "downside" of this ability is that the wielder needs to activate it with their venom manually.
Back when the world was still intact, Seniorious was also as "The Brown Dragon Killer", "The God Breaker" , and "The Secret Blade of the White Scabbard".
Known wielders of Seniorious include:
Lelia Asprey--20th generation Regal Brave, Willem's junior disciple. Adventurer level 71.
Chtholly Nota Seniorious--Fairy with sky blue hair. Main female protagonist of the Sukasuka anime series and Willem's lover.
(The following contains slight spoilers. Proceed at your own risk. You HAVE been warned):
In Chapter 4.5 in volume 5 also explain that Seniorious choose the people who accept that their hope can’t be true and use the power to create the new one. Even though it isn’t the same one as they want.
Known victims of Seniorious include:
The poteau (earth god) Carmine Lake.
The last visitor (star god) Elq Harksten.
Seniorious, like all Dug Weapons/Kaliyons, is made up of many talismans. In Seniorious's case however its talismans are all random and relatively useless. It is said that Seniorious was born out of a miraculous incident on the battlefield.