The Kuroi Yōroi is made of a mystic metal that is capable of repairing itself if broken, and which is attracted to other pieces of the armor. Five hundred years before the events of the series, the Kuroi Yōroi was worn by the Shredder when he and the Foot Clan spread chaos through Japan, during which it was said that it "swallowed [his] soul". When the Shredder was defeated by Splinter's ancestors, the armor was broken apart and spread across the globe so that the pieces would never be reunited, and the Shredder would not be revived.
One of the gauntlets was found in a jewelry store in a department store, where it was being used as a display piece for a ruby ring. Another gauntlet was lost by the Foot Clan during its recovery, and was instead found by Warren Stone, who discovered it increased the strength of one of his arms and allowed him to shoot energy blasts. While the gauntlet remained in Warren's possession for a time, it was ultimately retrieved by Baron Draxum, who had recently become an ally of the Foot Clan. The armor's lower greaves were found in the possession of Sunita (a slime yōkai befriended by April), who had been wearing them as boots.
In "Shadow of Evil", Splinter learned that the pieces of mystic metal that Baron Draxum and the Foot Clan had been gathering were in fact pieces of the Kuroi Yōroi, and unsuccessfully attempted to keep a piece of the chest plate out of their hands.