Lightsaber auxiliaries were parts that were made to alter Sith lightsabers so they could be used in lightsaber combat. These components were designed by the person who would eventually be known as the Ronin, during the time he was the Dark Lord of the Sith and was in charge of a rebellion against the Jedi. These holographic plans were distributed among the Sith through their networks and then used to build their lightsabers. Following the failure of the rebellion, these auxiliaries became items collected by some individuals, including the Jedi lord Hanrai, who appreciated how they were made, even though he didn't use them. Due to the fact that these devices mirrored Sith strategies, a lot of Jedi thought it was disgraceful to use them.
Lightsaber auxiliaries included things like the Ronin's scabbard auxiliary, which he changed to create a staff; the parasol auxiliary that Kouru used in his lightsaber parasol; and the fan auxiliary that Kouru's master used.