Justin Ballantine's early life was scarred by a series of mistakes concerning equilibrium. When he was eight years old, his mother died because of a faulty prescription. The local pharmacist was an alcoholic, and misjudged the amount of medicine she needed on his weighing scales. Justin's father became an alcoholic himself and frequently abused his son. Justin became fascinated with the stars as an escape from his brutal life. He used all of his money to buy a telescope so he could stargaze from his roof. One night his father met him on the roof and threatened to beat him with the telescope. However, he lost his footing and fell off to his death. Justin stared at his father's body until the police arrived, suddenly arriving at the notion that "life is a matter of balance". This notion became an obsession that defined his super-villain career.
Justin earned a scholarship to Opal University, and took physics classes under his personal idol Ted Knight (the first Starman). He was inspired by Knight's idea that stars possessed unlimited energy and used stolen copies of Knight's Cosmic Rod to create the "Energy Transmortifier", a machine that could steal half of the powers and/or energy of whatever it was used on.
Justin first appeated in Justice League of America # 111 and #112, and takes the name "Libra" as his code name. He is given control over the first incarnation of the Injustice Gang (Scarecrow, Poison Ivy, Mirror Master, Shadow Thief, Tattooed Man, and Chronos) by a mysterious benefactor who turns out to be the Apokoliptian New God Glorious Godfrey. Libra sends them to fight the Justice League and gives them special devices to activate in case they are defeated. The entire operation is revealed to be a crock when each villain uses their device in defeat; the devices are actually extensions of the Transmortifier, and Libra never planned for the Injustice Gang to defeat their opponents. Instead Libra uses the devices to steal half of the heroes' powers for himself, ranging from Superman's physical abilities to Flash's speed to Batman's intelligence.
Libra is satisfied with the test of his machine, and turns the Transmortifier on the galaxy in hopes of becoming a god. He gains half the "power" of the galaxy, but his body is unable to handle the acquisition of such an enormous amount of energy. He is absorbed into the universe, and his essence is dispersed as disembodied energy.
Libra is brought back into cohesion by Desaad on Apokolips. He meets Godfrey and pledges his eternal loyalty to Darkseid. It is implied that Darkseid turns Libra into a New God.
He appears on Earth at the beginning of Final Crisis and calls the Secret Society of Super-Villains to meet in Keystone City. Libra aims to become the leader of the Society by offering its members their hearts' desire in exchange for their cooperation. He preaches the idea that the heroes always win because they truly believe in the existence of "good" and offers a 'counter-religion', paralleling the cultish messages of the Religion of Crime (notably Libra seems to possess the Crime Bible, or a copy of it, during his meetings with the Society). This creates a rift between the groups' members: Lex Luthor and Doctor Sivana view Libra as a consummate hack trying to bribe his way into leadership, while others like the Human Flame and Clayface see him as genuine in his offer.
Libra leads the Society into drugging and killing Martian Manhunter, with the villain delivering the fatal blow. Soon afterwards the Society is confronted by the Spectre, who demands retribution for the execution. He kills Doctor Light by turning him into a candle, turns Effigy into lamp oil to burn in a facsimile of a Green Lantern's power battery, and hangs the Hangmen with ropes of energy. Libra successfully resists the Spectre's attempts to learn his true identity and drives him off with his own power. He also organizes the bombing of the Daily Planet by using Clayface to impersonate Jimmy Olsen, forcing Superman to stay by the side of his wife.
However, the Rogues reject Libra's offer of membership within the Society. He attempts and fails to recruit them by organizing a new group of "Rogues" and kidnapping various family members to use as bartering chips. After the Rogues kill Inertia, Libra reveals that Barry Allen is still alive and that he wants them to kill the Flash for Darkseid. They still say "No", but after hearing the news they decide to withhold retirement.
Libra arranges for a new headquarters (the former swamp headquarters for the Legion of Doom) and a new costume for the Human Flame as a sign of "his commitment to a higher cause". He forces Miller to wear a Justifier helmet, turning him into a slave of the Anti-Life Equation, before Luthor unexpectedly arrives to talk to him. He uses his new Justifiers to prevent Luthor's assassination attempt, as Luthor believed Libra is becoming too effective and a serious threat to himself, and forces Luthor to swear obedience to "the God of Evil". He then reveals himself to be a prophet of "the day of Apokolips".
He next appears at the public execution of Calculator. Libra has condemned Kuttler for "giving" the Resistance access to the Unternet, a 'hidden' Internet created by him through a secret eighth layer of the TCP/IP protocol, and and breaking codes for them. He gives Luthor the honor of leading the rearguard action at Bludhaven as a symbol of his loyalty. Libra declares the coming of the "night of anguish that lasts forever" as Darkseid comes into his full power and Earth falls through space and time. Libra then reveals his knowledge that Luthor was actually the one who gave the Resistance access to the Unternet, but Luthor has already made plans with Sivana to take control of the Society. Sivana uses a short-range transmitter to subdue and control the Justifiers while Luthor, who was allowed to power up his war-suit in preparation for the assault on Bludhaven, blasts a hole through Libra. Libra vanishes, only leaving his robe behind.
Powers and Equipment
Libra originally relied on his intelligence and manipulation of others. He tricked the Injustice Gang into confronting the Justice League in order to siphon off the League's powers. He designed a machine called the "Energy Transmortifier" which could steal half the power from any target, whether it was an individual or an object, and impart it upon the user. It was designed in the form of his staff, a long spear with scales at the end.
Libra's powers during Final Crisis are somewhat confusing, considering the nature of his enhancement was never clearly explained. It was hinted that he became a New God but he did not openly display the various powers exhibited by the more prominent New Gods (massive superhuman strength, durability, speed and reflexes; powerful energy manipulation and projection; matter transmutation; dimensional travel, etc.). Yet there are examples of New Gods such as Desaad and Glorious Godfrey who do not greatly differ from ordinary humans as well. Libra has also been referred to as "the Anti-Life that walks" by Godfrey, either a metaphorical nod to his role or a literal explanation of his transformation.
Some of his abilities have mirrored the effect of the Anti-Life Equation, and support the idea that he was a physical manifestation of it. Libra has shown extraordinary persuasion similar to Glorious Godfrey in convincing people to follow him. Simply by guaranteeing their hearts' desire he was able to divide the Society, perhaps importantly, between its more strong-willed/personally ambitious members and its lower-ranked members (even before he carried out his side of the bargain). During Final Crisis: Rogues' Revenge, Heat Wave needed to concentrate on fire in order not to fall under his speech. Pied Piper was able to transmit the Anti-Life Equation through his music, so it is possible that Libra was able to do the same through his speech. Libra as a living embodiment of the Anti-Life Equation may also explain his resistance to the Spectre's power.The Spectre has recently shown to be powerless against individuals who do not have souls (e.g. Nekron), so Libra may be not longer human or technically living (as the Spectre has been able to combat New Gods such as Darkseid in the past). It may be that Libra was under the protection of Darkseid, whose power and influence had grown so greatly that he could afford to overcome the Vengeance of God. When Luthor blasted him he completely vanished without a trace, prompting Sivana to remark that he would probably return.
Libra was able to see through Manhunter's telepathic illusions and could physically pierce his body with his staff; even while drugged, he should possess a base level of considerable physical durability. He may have still possessed the Transmortifier as a prophet of Darkseid, which may have allowed him to do this, but no clear indication was given during the story arc. Despite his powers, Libra was still a physical being with physical limits: Inertia badly beat him during Rogues' Revenge.
In other media
A slightly warped version of Libra, Equinox, appears on Batman the Brave and the Bold episode "When OMAC Attacks", as well as a teaser in a previous episode. In his appearances, his powers involve superhuman resistance, reality warping and others.