A brilliant but unscrupulous medical scientist, Dr. Calvin Zabo experimented upon himself in the hopes of creating a formula capable of augmenting a person’s physical strength and endurance. Realising he was unrecognisable in this new form, Mr. Hyde began operating as a criminal, often teaming with King Cobra. Since then, Hyde has clashed with many heroes, particularly Thor and Daredevil, but has been defeated and imprisoned nearly every time.
In his Hyde form, Zabo has tremendous superhuman strength, durability and recuperative powers, and an inhuman tolerance to pain. He must periodically ingest his Hyde formula in order to sustain or regain his Hyde physique. In either identity, he is a gifted biochemist. As Hyde, his personality is exceptionally savage and bestial in nature, though still intelligent.