Marshall D. Teech (マーシャル・D・ティーチ Māsharu Dī Tīchi?), later known as Blackbeard (黒ひげ Kurohige?), is the captain of the Blackbeard Pirates. As a member of the Whitebeard Pirates,[ch. 159] he kills one of his crew mates, Thatch, to get hold of the Devil Fruit he has sought for several decades,[ch. 440] the Dark-Dark Fruit (ヤミヤミの実 Yami Yami no Mi?). It grants him the ability to create and control gravity fields, which are represented as flowing darkness, as well as the ability to disable the Devil Fruit powers of others, as long as he is touching the person.[ch. 441] For betraying Whitebeard's crew and the murder of his crewmate, he is pursued by Ace who eventually confronts him.[ch. 159, 440] After defeating Ace and turning him in to the World Government, he is appointed the replacement for Crocodile as one of the Seven Warlords of the Sea,[ch. 486] a position he promptly abuses to expand his crew with prisoners from Impel Down and resigns once he's finished.[ch. 576] After killing Whitebeard with the help of his crew, Blackbeard somehow adds his former captain's Devil Fruit ability to his own and manages to take Whitebeard's place as one of the Four Emperors.