Its full name is Antebellum - Before the War, and it is supposedly crafted from the tooth of Hunter's ancestor, Hrethel Jusenkyou. The sword is extremly powerful, having the ability to draw energy from all around it to give to the wielder. It comes from an Alternate Timeline in which Hunter's mother, Sahar, does not die. In this timeline, they know of Samuel Fate's impending attack, and are preparing for it, but Hunter has not yet been made Pendragon.
'He came into focus clad in Slayer Dragon garb, but accentuated with the colors of the High Mountain Flight. There was a sword on his belt, but not Echbalder, it was a more curved, single-edged blade, similar to what he’d trained with at the Show-Lyn temple, but with a highly ornate handle in the shape of a dragon’s head.
As Hunter continued to walk, the apparitions fell away, and he was alone again, holding the other Hunter’s sword. He pulled it a few inches from the scabbard, feeling its power surge across his body. The blade was thick, thicker than a metal sword should be, but by its heft he could tell it was very light and perfectly balanced. The material gleamed and rivulets of magic flowed across its surface and formed into waves which broke against the hilt. The sheath was less a cover than a shield, stopping the weapon from drawing in power from all over and giving it to the wielder, and Hunter knew he should not pull it more than a few inches from it’s [sic] scabbard. But that few inches was enough to show him where the name was etched into the surface: Antebellum - Before the War'.
Antebellum translates literally to "before the war" so the swords name is in essence Before the War - Before the War. This is actually a hint of its role in the continuing storyline of the Course Books: it first originates from an alternate timeline where Samuel Fate's invasion has not yet happened (before that war), and is not seen again until the Consecution Books, wherein it appears shortly before a major campaign begins.
The name was suggested by a good friend of the author, who is mentioned in the acknowledgements in book 3 of the Course Books series.