Mongul was an absolute ruler over a planet believing that the only true way to rule is with an iron fist and was branded as a tyrant by them for his way of ruling. Eventually, the people went to the ancient Arkymandryte from the mountains and he preached to the people, and soon the people rebelled and Mongul was forced to flee for his life. Mongul later found out that this new ruler was an even bigger tyrant than he was, and believes people deserve whatever ruler they get and wishes to establish himself as ruler of the universe.
Superman encounters him one day when Mongul contacts him and commands him to obtain a crystal key for him, and shows that he has already kidnapped some of his friends so Superman has no choice but to get it for him. Superman learns that the planet on which the key resides on neighbors New Mars, home to the Martian Manhunter, and the Manhunter tells him he won't let him have the key because of the destruction it will bring as he narrates to Superman about how the key activates Warworld and how Warworld was built by a war-like race called the Warzoons, who wished to rule the universe. The Warzoons eventually all died out, and the last one was found dead at the command chair in Warworld. A peaceful race known as the Largas came to Warworld and buried the last Warzoon, but could not bring themselves to destroy Warworld and instead programmed its defenses so that no one will be able to step foot on Warworld ever again and made it so that one can only enter with the use of the vibrations of a special crystal key and gave the crystal key to the Martians before they all died out.
Superman, however, has friends at stake and fights the Martian, eventually defeating him regretfully, and takes the key from its crypt. Mongul then arrives and though Superman tries to fight him and keep the key away from him, he is too strong and takes the key, but not before the Manhunter frees Superman's friends from Mongul.
Superman and Supergirl then go to seek out Warworld, but as they encounter the giant star-sized battle station, they realize that its weapons, which include giant nuclear missiles and macro-laser cannons capable of destroying planets, are too much for even them. But soon, Superman remembers when he saw the Warzoons graves, they weren't buried in massive graves but rather one by one so they must have all died out one at a time and buried each other except for the last one who was buried by the Largas, and knows that the only thing on Warworld that could have killed them all one by one is the command chair, which they realized must put an extraordinary strain on the user's brain which ended up killing. Realizing this, Superman and Supergirl force Mongul to draw out all of Warworld's weapons, putting a large strain on Mongul's brain, knocking him out, and then they proceed to destroy Warworld, but not before Mongul escapes.
Superman first met the warlord Mongul while in self-imposed exile from Earth. Wracked with doubt over his ability to uphold truth and justice, the Man of Steel wandered through outer space and into the clutches of interstellar slave traders. Sold into the warlord's challenge arena, Superman bested Mongul's champions without ever delivering a killing blow, a defiance that would pit the Man of Steel against the emperor of Warworld himself.
Mongul's mechanized base was a weapon of mass destruction that roamed the cosmos, striking fear and terror with its awesome firepower. No army could stand against the might of Warworld. Entire planetary systems were left smoldering ruins as Mongul's snub fighters blitzed alien cities from the air, while giant battle tanks brutally crushed any lingering resistance beneath their spiked treads. Space Sector 151 was ravaged in a war against Mongul, leaving the Sector composed almost entirely of asteroids.
The Death of Mongul
The alien tyrant teamed with the Cyborg to devastate Coast City and transform Earth into a new Warworld. Mongul instead found defeat and incarceration. He was among scores of villains offered augmented powers by the demon Neron. When Mongul proudly refused, Neron sealed his fate. Though Mongul perished, his bloodline endured in two equally cruel children, a son who became a brief ally to the Man of Steel, and a daughter who still yearns to taste revenge in her father's memory.
Son of Mongul
Blackest Night Tales of the Corps #1
When ever his father would leave Debstam IV Mongul Jr. would sneak out of the castle and journey to the media center to watch old "digis" of his father's battle with the heroes of earth. Although, the way he saw it his father was the hero and these earthling's were the villains.
After watching for hours he'd recreate some of the battles using dead bodies as the earthlings. Then one day a small space ship crashed and Mongul Jr. enslaved its crew. He had them build a monument to him and he dress them up as the earthling's and spar against them. He kill one or two before his father caught him.
Mongul Sr was not happy and killed the aliens, claiming only he should be aloud slaves. then with on punch he destroyed his son's monument. After he father left Mongul Jr rebuilt the monument believing he too will have the power of his father.
Green Lantern Vol 4,
Mongul's son (also named Mongul) went to Earth to get revenge for his father. He battled Hal Jordan and the Green Arrow but was interrupted by his sister, Mongal. They were sent back to their home planet of Debstam IV where Mongul killed his sister, citing family as a weakness.
Fear Mongul! Sinestro Corps Leader
Status: Inactive, held within the Sinestro Corp Central Battery
Space Sector: 2811
Sector Partner: ?
Homeworld: Debstam IV
Mongul then comes across the injured Sinestro Soldier of Sector 2809 when the alien's ship crashes down on Debstam IV, located in Sector 2811. Mongul enters the wreckage and finds the fallen Sinestro Corps member. The injured man offers Mongul the power ring and Mongul breaks his neck, taking the ring anyway. Mongul's first act was to order his ring to inform him of all it's capablities. He then spent the next 96 hours learning all of the capabilities of his new weapon. After the ring is finished, Mongul asks it how many rings are currently seeking a bearer. After receiving the information, and the coordinates of said rings, he proceeds to berate his sister's skull before flying off to put his plan into motion.
Mongul next travels to Sector 226 and arrives at Clementia; the home planet of the Black Mercy plants. While taking time to remember his father, he sets about gathering some of the plants. He then heads off into space. Mongul sets about tracking down the rings that are seeking new bearers. As Duel Eknham is chosen by a ring, Mongul bursts into the hospital. He then proceeds to give the newest member of the Sinestro Corps the options of joining him, or relinquishing his ring in exchange for a Black Mercy. He has presumably encountered 5 other Sinestro's based on the fact he is now sporting 6 rings, and taking note of this fact Duel chooses to side with him. The two then proceed to slaughter the inhabitants of the hospital, sticking around long enough afterwards to ambush Sodam Yat and Arisia and take them hostage.
Mongul returns to the planet of the Mercies, with Duel, Sodam, and Arisia. He then begins to use his rings to dig to the center of the planet. He then began using them to change the Black Mercies, so that instead of showing a person's greatest joy, they would show them their darkest fears. He was forced to expend energy blasting Duel when the former ignored him about touching the Green Lanterns. He then proceeded to launch his altered seeds into the atmosphere towards other waiting planets. Mongul then, leaving the Lanterns behind under the influence of his altered Black Mercies, left for another part of the planet to collect more seeds.
While he was collecting seeds to further his plans, Mongul's attention was grabbed by his ring informing him in a change of the gravity of the planet. He almost wrote it off as feeding time for the Mercies, before he realized that it was localized to one area. Going to investigate he found not only more Lanterns, but Mother Mercy herself. He manages to ambush the Lanterns, blasting all of them with Mercies. Mongul then confronts Mother Mercy, angered by her "betrayal", he orders her to finish off the Lanterns. He then informs Duel he wants him to stay behind, causing yet another arguement. Tired of their squabling, he separates the two and leaves one behind, and brings the other with him. He then heads off into space to finish enacting his plan. He doesn't even make it out of the system before the Lanterns manage to confront him, having been set free by Mercy. He then proceeds to battle them to a standstill. Just as Mongul readies himself for another assault, he convulses. Bzzd bursts forth from his eye, having attacked him internally. The other Lanterns then proceed to blast him back into Mercies gravity well, who begins to feed him to her children.
Mongul later manages to escape the grasp of Mother Mercy, though his arm has been severed in the process. He flies away from the planet. He doesn't stop until he runs into a private ship carrying Kered and Miri Riam, blasting through it's shield and boarding it. He then proceeds to raid the available rations, before blasting his way out of the ship and continuing on his journey, leaving the two occupants to die in space. Mongul's next stop was a pleasure planet, when the owner of the establishment protested to his plans to enjoy their services, Mongul wasted no time in killing him. He then spent the night enjoying the women's company, and good food. He then continued on, making his way to the planet Daxam, though his plans for the people are unknown.
Mongul transformed the planet Daxam in the new base of operations of the Sinestro Corps. Mongul announced that he was now their leader.
However Arkillo challenged him to single combat without their rings (the winner of this battle will be the new leader of the Sinestro Corps). Arkillo is a tough opponent for Mongul, but in the end Mongul wins (Ripping Out Arkillo's tongue) - After the match against Arkillo, Mongul gains complete mastery over the planet Daxam and the Sinestro Corps.
Sodam Yat and Arisia decided to investigate the situation. Sodam Yat kills some members of the Sinestro Corps. Sodam Yat frees his father and decides to fight Mongul. Sodam Yat surprises Mongul and fight bravely. In the end, Sodam Yat decides to enter Daxam's Red Sun
Sodam Yat turns Daxam's Red Sun in a yellow star, giving super powers to all the inhabitants of the planet Daxam. Mongul leaves the planet Daxam along with the other members of the Sinestro Corps (Mongul says that "things got more interesting"). After his defeat on the planet Daxam, Mongul installs itself on Planet Korugar.
Indigo-1 carries Sinestro to Korugar to defeat Mongul. Mongul and Sinestro are fighting for control of the Sinestro Corps. Mongul took the advantage in combat, Mongul says to Sinestro that he is a being of Action. And proceeds to beating up Sinestro.But in the end, Sinestro Override his ring thus finally defeats Mongul .Sinestro then imprison Mongul in The central power battery (Green Lantern Vol 5 # 46)Mongul fate remain unknown.
Mongul The Elder( aka Mongul Sr. ):
Mongul the Elder had Physical Strength greater than Superman; in fact Superman was only able to beat him in a fight once, while Mongul himself overwhelmed Superman numerous times. Mongul has also beaten Hal Jordan, Supergirl, & Martian Manhunter with just pure brute force, and broke out of the hardest material in the universe with ease.
Mongul The Elder was almost invulnerable to nearly all types of harm. Wonder Woman hurt her own hands just punching the War Lord's face.
Mongul also had an energy cannon on his chest, and was able to to fire energy from his eyes and hands. In addition, Mongul had limited telepathy and telekinesis.
He had the ability to teleport, though for a long time was unknown whether it was an actual ability or own caused by technology, until after a battle with Superman & Starman damaged his costume; he managed to get away from them by teleporting.
He commanded numerous arrays of technology including dimensional inversion cubes, and the planet-sized engine of destruction War World.
Mongul Sr. was also a very intelligent and cunning foe, but even more dangerous than either his intellect or physical stats was his complete and total lack of respect for life. He had little to no respect for other beings' lives and would do anything to accomplish his goals, even destroying entire worlds.
Mongul Sr. was also a superb combatant able to take on entire teams of heroes alone and still come out on top.
Mongul II ( aka Mongul Jr. ):
Mongul has physical strength to fight on equal terms against Superman. Mongul has enough physical strength to defeat Wonder Woman (Infinite Crisis issue 1, Mongul defeats Wonder Woman effortlessly).
Mongul also has a magnificent durability (Mongul withstood several blows from Superman).
Mongul has a powerful energy cannon (the cannon is located in the chest). This cannon fires powerful bursts of energy.
After the Sinestro Corps War, Mongul got a Qwardian Power Ring. Mongul killed several members of the Sinestro Corps (Mongul got more rings). Mongul also seems to be very talented with the rings, as he able to battle nine veteran Lanterns at the same time and still hold the advantage. Aside from his physical prowess and power rings Mongul is a very skilled combatant.
In other media
Mongul appears in the Justice League episode "War World" where he is voiced by Eric Roberts. He forcefully coerces Superman into fighting for him in Gladiator-style matches, providing entertainment for the masses. Ultimately, however, he is defeated, and consequently humiliated, in single-combat by Superman and Draaga.
Justice League Unlimited
Mongul traps Superman in The Fortress of Solitude on Superman's birthday using Black Mercy plant. His Voice work was once again provided for by Eric Roberts from Justice League, Mongul returns to claim revenge on Superman by killing him and taking the Earth under his tyrannical rule. After totally beating down Wonder Woman effortlessly, and tossing Batman aside like a ragdoll, Mongul got into a brutal battle with the Man of Steel, gaining an upper hand he was going to finish off Superman until Wonder Woman tossed the Black Mercy onto him trapping him in his own dark twisted Fantasies.
DC Original Animated Movies
Mongul appears in the animated film - Superman/Batman: Public Enemies in 2009. His voice/grunts were provided by Bruce Timm. He was one of the super villains trying to grab the bounty placed on Superman's head. After a short battle with Superman he was defeated. However it was revealed that he was being mind controlled by Gorilla Grodd cause Superman noticed he wasn't his usual talkative self, and that he heard a Gorilla's Heartbeat..
Batman: The Brave and the Bold
He appears in "Duel of the Double Crosses". Where he uses Jonah Hex to capture warriors to fight in his Warworlds who he sets up a deal with. Hex captures Batman and brings him to Warworld. Mongul goes back on his word so Jonah helps Batman defeat Warworld's champion. Hex and Batman then frees the prisoners who then attack Mongul.
He also appears in "Death Race to Oblivion". In this episode he pits heroes and villains against each other in race to the death. In the end he is outsmarted by the heroes and defeated. He is voiced by Gary Anthony Williams.
Mongul appears in the second season episode "War", where he is voiced by Keith David. While at the interplanetary trial for the Justice League members that attacked Rimbor (while under the control of the Light), he is urged on by Vandal Savage (who is also secretly at the trial) to go and conquer the Earth, after everyone at the proceedings learn that the Reach has taken the planet. Mongul brings War World to Earth and begins unleashing attack after attack using its vast array of weaponry, only to have his attempts thwarted by Captain Atom, Captain Marvel, Doctor Fate, Rocket, Green Beetle, Robin and Batgirl (in the bio-ship), and a wave of Reach ships. Mongul himself faces Superboy, Wonder Girl, Wolf, and Arsenal, who are a part of an infiltration effort by the Team (Blue Beetle, Impulse, and Beast Boy go after War World's key, while Bumblebee and Mal Duncan (in the Guardian's exo-skeleton) shut down War World's core). When Bumblebee sends the power of the core straight to Mongul's control room, the overload stuns Mongul long enough for Superboy and Wonder Girl to knock him out cold.
In the X-Box Exclusive game, Superman: Man of Steel, Mongul is one of the villains to appear in the game. Along with his War World. His is voiced by James Patrick Stewart.
In the Movie tie-in video game Superman Returns, Mongul once again appearing on War World and Metropolis accompanied by two video Game exclusive gladiators, Phaltune & Overkhast make life hard for the Man of Steel. He is voiced by Todd Williams.
In the Batman: the Brave & The Bold : The Video Game, Mongul appears as a boss character. His voice is once again provided for by Gary Anthony Williams.
Numerous toys and action figures have been released based on Mongul and his different incarnations.
Mongul was ranked #41 on IGN's Top 100 comic Book villains of all time list.