The Medusa Mask can manipulate the emotions of others, matching the appearance the mask takes (sad face, happy face etc.). It is the source of the Psycho-Pirate's powers.
Charles Halstead, the first Psycho-Pirate, had imagined and divined the existence of several golden faceplates with the power to influence others' emotions. He longed for a successor in the arts of crime related to emotions, and so chose to impart this knowledge onto his cellmate, Roger Hayden. Hayden located the masks after Halstead's death and, for a time, wielded them separately as the new Psycho-Pirate. He later decided to merge all of the masks into one, giving him the power of the whole Emotional Spectrum with a single mask. He succeeded in his endeavors, but the united mask had the sad problem of inflicting a form of emotional vampirism upon the wearer, forcing him to drain emotions to sustain himself.
He wore this mask during the Crisis on Infinite Earths, the Infinite Crisis and the Last Laugh riots. During Underworld Unleashed, this mask was bonded to him and its metal largely replaced half of his brain. For a brief time this expression of Neron's "gift", revealed itself as a golden, gleaming eye patch over his left eye. The mask also held the power to summon any of the people who had died during the Crisis of Infinite Earths, but the strain removed Hayden from reality.
Later, during the time Hayden was resurrected as a Black Lantern, Conner Kent discovered the mask had a harmful influence upon the members of the Black Lantern Corps. He was able to destroy Black Lanterns Roger Hayden and Kal-L by forcing them to experience all emotions with the mask. The emotional blast severed the connection between the corpses and the rings, leaving them inert again. Unfortunately, the escaping rings shattered the mask, destroying it.
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