Lord Malvolio is the son of a human woman and the Green Lantern of Sector 1634. Born in 1612, his mother died in childbirth, and Malvolio was raised by his father. Eventually, he slew his father and took his ring, traveling the stars until he came upon his father's planet. When the Guardians of the Universe learned of the Lantern's passing, they named Priest the new Green Lantern of Sector 1634, and sent him to slay Malvolio. When Priest refused to slay him, opting instead to imprison the false Lantern in a starless void, he was stripped of his title. Malvolio languished in his prison until the present day, plotting.
After meeting and assisting Priest with a border war, Hal Jordan was pursuing an alien that had inadvertently caused massive destruction on Earth, when he found himself teleported to Malvolio's system. Jordan ran across an alien scientist and asked if he might know the way back to Earth; the scientist suggested he consult his "master". A short time later, Jordan found a citadel, perched on a mountain marked with a Green Lantern symbol; inside, he met Lord Malvolio, who revealed that he too was from Earth, and made cryptic reference to Phobus. Not gaining any answers, Jordan went back to the scientist, when Malvolio suddenly appeared and murdered the alien. Malvolio revealed that he had brought Jordan there, looking to make him his heir; the two battled, and Malvolio blasted Jordan through the planet. Jordan fled to a strange yellow satellite, and was surprised to find a large number of aliens worshiping a Power Battery. He met a man named Wallace, who claimed to be Malvolio's squire.
Jordan was surprised to find out that the satellite he thought was meant to be a sanctuary from Malvolio, was in fact a shrine in his honor. Arriving on the scene, Malvolio destroyed the satellite, killing everyone inside. The battle resumed, and Jordan managed to gain the upper hand. He turned to walk away, when Malvolio pulled a weapon. Jordan turned to blast the gun from Malvolio's hand, when it fired, destroying his ring. Jordan fled and managed to find some weapons. Using a brace and tension rod as a bow and arrow, he fired a shot into Malvolio's chest, seemingly killing him. Jordan took Malvolio's ring and used it to return to Earth.After he left, Malvolio stood up and pulled the rod from his chest; his surroundings disappeared, an illusion created by Malvolio himself. Malvolio mused that the entire encounter was a ploy to get Jordan to use his ring, in an elaborate plan to get revenge on Priest and the Guardians. Malvolio's ultimate end game has yet to be revealed.
Jim Owsley, now Christopher Priest, has stated that DC has no interest in the character, which is why the storyline was dropped. The character's name has come up in conversation, but has yet to be reintroduced into continuity.
Malvolio was never actually a member of the Green Lantern Corps, as he took his father's ring rather than being inducted.
Before the Parallax story the fact that Hal was wearing Lord Malvolio's ring when he went crazy was a popular way for Hal fans to explain why Hal went crazy.
Given that Kyle's ring was a reformed version of the ring Hal wore when he went nuts (presumably Lord Malvolio's ring) this would also explain Oblivion