The Black Guardian, also known as the Guardian of Darkness and Chaos, was an anthropomorphic personification of the forces opposed to the powers of light, as embodied by the White Guardian. With the White Guardian and four others, he was part of the Six-Fold God known as the Guardians of Time.
Like all Guardians, the Black Guardian was the embodiment of chaos in time. He was only as powerful as his element in the universe. He was able to change his appearance at will and channel his power of destruction to his followers.
Activities on Earth 1337-A
The Black Guardian was responsible for the resurrection of The Corruptor as a Khadi in the flesh of one of Doctor Xadium's alternate selves. He was badly wounded by Hazel Ninegate, who took a fair portion of his powers, which he has already begun to recover from.