Among swords wielded by humans, two-weapon fighting is a rare technique, for there are few swordsmen with the ambidexterity and hand-eye coordination to fight effectively using this style. But without the limitations of a human to control them, two swords have an advantage over one, and replicating themselves into a Doublade is an extremely effective way for a Honedge who has mastered single-sword fighting to increase its chance of victory.
Although Doublade are composed of two swords, there is a single spirit between them, albeit split into two halves to better control their blades. Doublade master techniques they could never accomplish in life as a single blade with a wielder. However, Doublade did not go to war even back when swords ruled the battlefield, for although fighting two soldiers at once was an impressive feat, the chaos of massive melees does not allow these ghosts the individual glory they desire. Instead, they competed at tournaments, and defeating one while living, then as is those competitions' modern descendants, was considered to be the proof that one was a master swordsman.
In life, many of those whose spirits would become Honedge regarded Doublade not with pity or malice, as most ghosts are regarded by the living, but with envy, for those who faced them were almost always unable to triumph in battle. The inability to move onto the next world can be a tragedy, but it need not be; sometimes, as with the Doublade, becoming a ghost is simply a way to exceed mortal lifespans in an unending and exciting quest for glory.