José del Carmen Castillo Aguilera was a Mexican luchador known as Leon Negro. "Leon" because he was from León Guanajuato; and "Negro" because of his dark complexion.
Although, most of his career was at small arenas, he made seasons with the Coliseinos and in the Independientes. At Arena Coliseo almost everyone knew that León Negro was brother of the former World Bantam Boxing champion, Chucho Castillo who was one of the few who could defeat Ruben "Puas" Olivares.
Among his achievements, he won the masks of Carta Brava and Rey Volador. In August 26, 1978 at Palacio de los de Deportes, in the same event in which Canek defeated Lou Thesz in a Championship match; Ultraman won Leon's mask.
