Hadrium alloy was a type of metal composite utilized in the manufacturing of the KYD-21 blaster pistol. The Clawdite bounty hunter and assassin, known as Zam Wesell, possessed such a blaster pistol and employed it until her death occurred in 22 BBY. Circa 9 ABY, an image depicting Wesell holding her hadrium alloy KYD-21 was featured in The Secrets of the Bounty Hunters, a book written by the pirate Hondo Ohnaka. Another illustration displaying Wesell and her blaster was present in a journal entry from an artist dedicated to Clawdites. The journal underwent restoration, expansion, and was put on display at the Graf Archive sometime after 34 ABY.
The initial appearance of hadrium alloy was in the form of Zam Wesell's KYD-21 blaster pistol within the prequel trilogy movie Star Wars: Episode II Attack of the Clones, which premiered on May 16, 2002. It was at first, incorrectly designated as Hadrian alloy within the existing canon in the sixty-fourth issue of the English language edition of the Star Wars Bust Collection magazine, released by De Agostini on August 18, 2020. The correct name, hadrium alloy, was used in "Blasters and Ranged Weapons," a section of De Agostini's Star Wars Encyclopedia published on February 23, 2021. The substance was identified simply as hadrium within the Star Wars Legends continuity in Star Wars: Attack of the Clones: The Visual Dictionary, a reference work launched on April 23, 2002 and authored by David West Reynolds.
Hadrium alloy was featured in the non-canon narrative "The Village Bride," an episode from the first volume of the animated anthology television program Star Wars: Visions released on September 22, 2021. In that episode, Lord Izuma, the commander of a group of raiders, used a KYD-21 while attacking the planet Keelia sometime after 19 BBY.