Jadoku

Jadoku, the Ancestral Sword of the now-defunct Snake Clan, was gifted along with a matching wakizashi to Snake Clan Champion Isawa Chuda by the Emperor himself. After discovering that his wife was a maho-tsukai, Chuda fled his clan, taking only Jadoku with him and leaving the wakizashi (whose name has been lost to history) with it.

Jadoku was last seen in the Empire in the early days of the Clan War, when Reikado, a ronin descendant of Isawa Chuda and Chuda Tenkazu, a powerful Bloodspeaker living among the Asako family, met in battle. The resulting conflict almost destroyed the Falcon Clan and ended with Tenkazu reuniting the daisho after Reikado fled. Neither blades have been seen since.

Major References
Magic of Rokugan, p. 65. Secrets of the Shadowlands, p. 27, 33.