Born and raised in Japan, Carl Sands used the ninja skills he learned as a boy to become a professional thief. Hired by renegade Thanagarian police chief Byth to steal the ship of then Hawkman and Hawkwoman Katar and Shayera Hol, Sands was given a special suit that transformed him into a living shadow, allowing him to slip into closed areas with ease. After being defeated time and again by both the Silver Age Hawkman and his predecessor the Golden Age Hawkman, Sands sold his soul to the demon Neron for greater powers. Both even with these abilites, Hawkman manages to show Shadow Thief the light of justice. (The whole him being the manifestation of Hawkman's inner darkness was only canon to Justice League Unlimited).
In shadow form, Shadow Thief is two dimensional and intangible. He can also turn people and objects into shadows.
Batman Brave and the Bold
In the episode "Sidekicks Assemble" The League talks about a meteor heading for Earth. Green Arrow then suggests that Shadow Thief may be behind it.
In this show he is hired by Black Mask to break him out of jail and to help him fight Batman. Altough he manages to beat Batman at first he later gets defeated by him.