Material-D is a Material—essentially a magical clone—created from Hayate Yagami during the Dark Fragment Incident. She's part of the Unbreakable Dark system.
The "D" in her designation stands for "Darkness," a fitting nod to both Hayate's connection to the Book of Darkness and her own nature. Her full name is Lord Dearche, though she goes by just Dearche in most contexts. English releases first introduced her as "Material-D," while the original Japanese called her "Lord Ruler of Darkness," though without the proper name formatting that would come later.
Her official name didn't get fully clarified until The Gears of Destiny revealed the ruby text spelling: "Lord" Dearche. The Innocent video game properly standardized it as "Lord Dearche." (There's some debate whether the English "D" was ever meant as a straightforward abbreviation or something got lost in translation, but the Japanese name has always been consistent.)
Her magical device is Yersinia Kreuz.
Content compiled by AnimeList.moe from publicly available sources.
