A huge, yellow-skinned, enormously powerful alien warlord who is driven by two goals: the desire for conquest and an obsessive thirst for revenge against Superman.
Powers: Mongul possesses an extraordinary level of super-strength that seems to be equal to that of Superman, witnessed by the fact that he has repeatedly fought the Man of Steel to a standstill. In addition, Mongul is invulnerable to nearly all forms of physical harm, and is able to project extremely potent energy bolts from his hands that are powerful enough to stagger the Man of Might. Mongul also seems to possess a limited capacity for telepathy, and the ability to teleport himself across even interplanetary distances. Mongul seemingly has the capacity to create dimensional-inversion cubes, designed to prevent escape by warping their interior reality and absorbing any power used against them from within. Whether this is an actual power or merely a sophisticated technological device is unclear.
Biography: The only known fact about Mongul's early life is that he was once the merciless dictator of an entire world until an ancient holy man called the Arkymandyte appeared and incited the general population to revolt against his rule. The revolution proved successful, and Mongul was forced to abandon his world and flee into space in order to save his own life. Because of this, it is generally assumed that Mongul aquired his vast powers at some point after his exile and before his first encounter with Superman, otherwise he would have been able to use them to put down the revolt against his dictatorship. The origin of Mongul's powers is also a complete unknown.
Sometime after he had gained his fantastic power, Mongul learns of an ancient crystal key created by a deceased alien race that can give him control of the immensely powerful battle station called Warworld. This key was secreted within a crypt on the fourth planet in the Cygnus star-system, a world commonly known as Mars II and the "second home" of J'onn J'onzz, the Martian Manhunter (who had, at the time, been charged with the key's protection), and his race. Apparently, J'onn had encountered Mongul before and thwarted an attempt by the rogue warlord to gain possession of the key. Seeking a pawn who was powerful enough to defeat the Manhunter and retrieve the key, Mongul journeys to Earth and kidnaps Lois Lane, Jimmy Olsen and Steve Lombard in order to coerce Superman into serving him. Superman does obtain the key, but refuses to hand it over to the alien would-be conqueror. When Mongul engages Superman in personal combat for possession of the key, the villain proves to be one of the Man of Tomorrow's most dangerous opponents, nearly besting him before finally escaping with the key (DCCP No. 27/1, Nov 1980: "The Key That Unlocked Chaos").
Eventually discovering the location of Warworld, Mongul uses the key to lay claim to the war machine and begin preparations to use it to re-conquer his lost world and spread his rule across the universe. Before he can put his plans into motion, Mongul encounters resistance when he is tracked down by both Superman and Supergirl. Cybernetically linked to Warworld's vast array of extraordinarily deadly weaponry, Mongul launches a devastating attack on the two heroes using the station's arsenal of ultra-powerful missiles. However, the super-cousins use Mongul's cybernetic interface with the Warworld's systems against him, causing him to pass out from the tremendous mental strain of controlling all of Warworld's weaponry in his continued assault. Despite his defeat, Mongul manages to recover in time to escape after Warworld is disabled after Supergirl destroys the war machine's central computer core (DCCP No. 28/1, Dec 1980: "Warworld").
Mongul next appears on the Throneworld of the interstellar empire known as the Infinite Realm, the ancestral home of Starman. Mongul murders Empress Clryssa, Starman's sister, and forces Starman's love Merria to marry him in order to usurp the throne of the Infinite Realm for himself, planning to use it as a staging ground for yet another attempt to retake the world of his first rule and build an intergalactic empire. To prevent Starman from interfering with his rule, Mongul imprisons the cosmic hero in a dimensional-inversion cube. In addition, the alien warlord takes control of Throneworld's doomsday device, located within Throneworld's sun and able to turn the star into a supernova if triggered, destroying the worlds of the Infinite Realm in the process. Superman arrives in the Infinte Realm and frees Starman by shattering it with his heat vision. Starman then joins the Action Ace in opposing Mongul and freeing the empire from his rule. While Starman disables Throneworld's doomsday device, Superman engages Mongul in one-on-one combat for a second time, a battle which turns out to be inconclusive after Starman arrives on the scene and Mongul is forced to retreat instead of facing both heroes and the empire's forces (DCCP No. 36, Aug 1981: "Whatever Happened to Starman?").
By this time, Mongul has developed a deep hatred for Superman and a burning desire to see the Man of Steel suffer greatly for his repeated interference in the alien conqueror's plans. To that end, Mongul journeys to the outer reaches of the universe and encounters one of the extradimensional Controllers, who has in his charge an incredibly dangerous Sun-Eater (it should be noted that this was not the Sun-Eater that nearly destroys Earth in the 30th century, but an equally deadly twin). Mongul murders the Controller and assumes command of the Sun-Eater using specialized control devices that are built into his uniform, and sends the monster on a direct course for Earth's sun. When the Man of Tomorrow attempts to put a hault to Mongul's machinations, the extraterrestrial warlord traps him in a specialized dimensional-inversion cube that is fueled by red solar radiaiton and thus begins to rob Superman of his super-powers. Mongul intends for Superman to watch helplessly as he directs the Sun-Eater to consume Earth's sun, thereby extinguishing all life on the planet, before Superman himself is to be finally killed. Although Mongul comes under attack by Supergirl and several members of the Justice League of America, Mongul is able to draw upon the Sun-Eater's virtually limitless destructive power to defeat them all. In a final desperate gamble, Jimmy Olsen (while watching the entire drama unfold from an observatory on Earth) uses his Legion flight ring to summon members of the Legion of Super-Heroes from the 30th century to aid Superman in saving Earth and subduing Mongul. The Legionnaires succeed in freeing Superman from imprisonment and manage to discover a means of destroying the Sun-Eater. Superman (driven by determination to protect his adopted home at any cost) finally bests Mongul in single combat (DCCP No. 43, Mar 1982: "In Final Battle").
Mongul is last seen when he launches a most insidious plan of revenge against Superman, attacking the Kryptonian in his own Fortress of Solitude on his birthday. Mongul manages to maneuver Superman into exposing himself to a plant-like entity called a Black Mercy by disguising it as an anonymous birthday gift. The plant promptly attaches itself to the Action Ace's chest and begins feeding on his bio-aura while keeping him in a trance-like state by providing him with a mental illusion of his mind's desires. In Superman's case, the entity makes him believe that Krypton has not exploded, and that he is happily married with a family on his home world. Although Mongul meet resistance when Batman, Robin and Wonder Woman arrive at the Fortress and discover the unfolding drama, Superman remains in his catatonic state, his "heart's desire" gradually degenerating into a twisted nightmare as the imaginary Krypton slides into social chaos. Signs of this decline include Kara being attacked by violent opponents of the penal use of the Phantom Zone and the embittered Jor-El making an inflammatory reactionary speech that incites a bloody riot. While Wonder Woman valiantly (but vainly) engages the hulking alien in combat, Superman's increasingly nightmarish experience weakens the Black Mercy's effect enough for Batman to succeed in removing it from his chest. Enraged at having been so violated, the Man of Tomorrow ferociously attacks Mongul. Fueled by intense feelings of grief and anger, Superman manages to gain the upper hand and is about to kill the alien warlord when the memories of his "dream" cause him to hesitate. The conqueror meets his final defeat when Robin uses special gauntlets that Mongul had employed in handling the Black Mercy to attach the plant to Mongul's own chest. As far as is known, Mongul remains in the thrall of the Black Mercy, completely immobile and dreaming dreams of endless bloody conquest (SA No. 11, 1985: "For The Man Who Has Everything").