Zoltan is said to be one of the finest blacksmiths in all of Fódlan, having crafted blades of the highest quality and sharpness.
Felix discovers one of his blades among many common made blades and purchases it. During his B-Support with Dimitri he shows off the blade, which Dimitri immediately notices is one of Zoltan's swords. Despite desiring to at least swing the sword once, Felix denies the request, fearing that Dimitri would break the sword like he used to in his youth.
The player must reach this support level to receive a copy of the sword.
Another way to get the sword is to kill Petra in Azure Moon: Chapter 21, during Verdant Wind: Chapter 21 from a chest, or Silver Snow: Chapter 20 by defeating a specific enemy after enough time has past.