This is a list of all Voltron enemies for the Defenders of the Universe series.
Main Article: Drule Empire
- Emperor Zeppo: Through most of the series, all we ever see of Zeppo is a portrait of him adorning every Drule command ship. It is not until much later that he is introduced in the flesh, attending meetings of the Drule Supreme Council. No other Drule holds higher royal rank than the Emperor. When the liberation of planet Drule finally came, Zeppo quietly stood by as Hazar personally overthrew his rule. Hazar thus immediately became Drule's rightful emperor, though he then decreed that their world would no longer have any Emperors, but that leaders would from then on be elected. Zeppo and Throk proceeded to quietly flee the dying planet. Shortly after the inevitable destruction of planet Drule, the liberated citizens were moved to a new planet by the Galaxy Alliance. As soon as they settled in, Zeppo and Throk set up a decoy to distract the Voltron Force, while the remnants of the Drule Empire swept in on the planet and retook control of their people. Emperor Zeppo was in control again. This possibly would have led to a second season of the Vehicle series, had WEP decided to animate their own episodes of it, as they had with the Lion Force series.
- Viceroy Throk: Possibly the worst of the worst, Throk is at bitter ends with Mozak and Hazar, and the loyalist supporter of Emperor Zeppo. Throk becomes the main baddie under Zeppo towards the very end of the series, especially during the impending arrival of the Voltron Force on the planet Drule to aid Hazar in liberating the homeworld, and overthrowing Zeppo. Later, Throk would join forces with Zarkon in building the universe's most feared space armada, the Fleet of Doom.
- Commander Hazar: High-ranking warlord of the Drule Empire. At the beginning of the series, he was a typical Drule leader bent on galactic conquest. However, midway through the series, he begins to have a change of heart, and becomes more compassionate in his quest; and, like Commander Hawkins, tries time and time again to arrange for peace between the Drule Empire and the Galaxy Alliance. Throughout the series, he has had to put up with demotions, imprisonment, and worst of all, treacherous underlings who repeatedly and deliberately disobey his direct orders of helping bring peace, in favor of attacking the Alliance.
- Dorma: Hazar's kindhearted sister, who appears towards the end of the series. When she is kidnapped by the Drule U.R.F. (Underground Rebel Force), she agrees to join in their fight for peace and freedom on planet Drule.
- Chancellor Mozak: Hazar and Dorma's father, and kindhearted member of the Drule Supreme Council, he wishes nothing more than for peace and freedom on planet Drule. He often clashes in his views with Viceroy Throk.
- Captain Mongo: One of the Drule Empire's best officers, and loyal friend to Hazar. When Hazar began to have a change of heart, Mongo was one of the few Drules who supported him, and he continued to loyally support him, until he eventually went into exile midway through the series.
- Bakki: Founder of the U.R.F., Bakki is a kind-hearted Drule, who hopes to liberate his homeworld's citizens from the tyranny of the Drule rulers.
- Commander Quark: An early opponent of the Explorer and its crew. Persistent, but ultimately ineffective against the Voltron Force. He causes the destruction of an uninhabited planet that the Drules and humans were competing over. Curiously, his death scene is included in the American Voltron release, but the scene was incongruously dubbed over, with Quark saying, "I'll be back," before his ship explodes. A member of the Voltron Force later states, "Quark got away again."
- Captain Nerok: Cruel and heavyset Drule officer. A natural-born kiss-up and backstabber, he lives for nothing more than destroying the Galaxy Alliance and making Hazar look like a fool.
- Marshall Keezor: Wicked and crafty member of the Drule Supreme Council. He first arrived personally to give Hazar the news of his demotion, then appeared to take on Hazar's duties of eliminating the Voltron Force. In the Lion Voltron series, it was also Keezor who arranged for Zarkon to be stripped of his powers and to have those powers handed over to Lotor.
- Captain Twyla: A female Drule officer who is captured by the Explorer crew. She is confused by Commander Hawkins's treatment of her as a guest instead of a prisoner. Hawkins explains to her that willingness to discuss peace negotiations is not the same thing as selling out her race. Her final fate is unknown, but Hawkins hoped that she communicated a new alternative to other members of her race.
- Zandu: A Drule pilot who is captured by the Explorer crew. Commander Hawkins, in usual form, treats the pilot as a guest instead of a prisoner. However, this upsets Shannon, a member of the Voltron Force Sea Team, who has a brother being held prisoner by the Drules. Shannon, upon getting to know Zandu, realizes that Zandu, despite being on the side of the enemy, is only following orders and unaware of the evil nature of his masters. Zandu is allowed to return to his ship, but is shot down by a Drule commander, who believes it is a trick by the humans. In the American version, he crashlands on a planet and though badly wounded, apparently survives. As is the usual case, he dies in the original Japanese version.
- Robeasts: Monsters of the Drule Empire that they send to fight the two Voltrons of the Galaxy Alliance.
The villains who are from Golion or the Korean animated episodes featuring the Voltron Lion Force, ruled by King Zarkon.
- King Zarkon (Emperor Daibazaal): King Zarkon of the Planet Doom is one of the rulers of the Drule Empire, though by no means the absolute ruler. He is constantly using others as scapegoats for his own failures (à la Zanbazir using Prince Heinel as a scapegoat), including his son Lotor. In the Japanese version, however, he is the evil ruler of his own Empire, without anybody controlling him. This differs from the American version, where he is a king with a Senate advisory body, with none daring to oppose him; very similar to Voltes V 's Emperor Zanbazir in his treatment of slaves (ex. whipping, starving, killing them on the spot, which is typical in super-robot shows). In the Japanese version, his character was eventually killed by GoLion. Zarkon was voiced by Jack Angel (US) & Kousei Tomita (Japan). In Voltron: The Third Dimension, Zarkon managed to redeem himself prior to his final defeat, and became a member of the Galactic Council. His redemption, however, was a ruse by which he and his son worked together to take over the alliance. In this version, he was voiced by Kevin Michael Richardson.
- Prince Lotor (Prince Sincline): Prince Lotor is the evil son of the Drule King Zarkon. He dislikes his father greatly, and wishes to rule in his place with Princess Allura by his side, to whom he has developed a strong and obsessive attraction. Like some supervillains who follow the cliche-but-adorable idea of a villain falling for a beautiful girl, Lotor is often shown commenting on how good a Queen she would be or how beautiful she is. So powerful is his attachment that he is unable even to destroy a holographic image of Allura. Lotor also has an even stronger hatred with Keith, because he's seen Allura's love towards Keith. Because of Allura and Keith's love, Lotor is more determined to kill Keith than any other Voltron Force member. Lotor is a very sly, smart, smooth, powerful man, who exudes force and emanates what seems to be pure evil, except when Allura is around. In GoLion, Sincline's obsession with Farla occurs because she resembles his mother, whom Emperor Daibazaal (a.k.a. King Zarkon) had killed for refusing to marry him after Lotor was born, with Princess Farla/Allura becoming his major psychological weakness. This is basically an Oedipus complex. Lotor was killed in the last episode of GoLion, something that is typical for super-robot shows. Lotor was voiced by Lennie Weinrib (US) & Akira Kamiya (Japan). In Voltron: The Third Dimension, Lotor was mortally wounded in a battle, and was converted into a cyborg after he was placed in prison. However, he escaped and perpetrated his revenge on the heroes, though he still has feelings for Allura. In this version, he was voiced by Tim Curry.
- Queen Merla: A villainess exclusive to the U.S. version, she was voiced by Tress MacNeille. Zarkon intended to have his son Lotor and Merla marry, but it didn't work out.
- Witch Haggar (Honerva): Haggar the witch is the one responsible for creating all of the Robeasts (or Galran Beast Fighters) Voltron must destroy. She is notorious for using her dark magic to cast hypnotizing spells over people. Though she was once good and beautiful, she is now evil and ugly. It was Haggar who was responsible for originally splitting Voltron into five components in the American version. In the Japanese version, she is hinted to be secretly Daibazaal's mother making her Sincline's grandmother. Haggar's voice was played by B.J. Ward (US) & Masako Nozawa (Japan). In Voltron: The Third Dimension, Haggar went into hiding after the final battle, but rejoined Lotor in his conquest schemes. They strike a deal in which, if Lotor conquers the universe, she gets the magic of the lions while he gets the universe and the lions themselves.
- 'Cova: Haggar's blue cat, enemy of the Space Mice.
- Commander Yurak (Sadak): Commander of the Galran/Doom Forces. In both versions, he is sentenced to death. He is transformed into a gigantic beast fighter in hopes of redeeming himself. However, he is killed by GoLion/Voltron. Yurak's death is one of the few onscreen character deaths that were retained for the American Voltron release.
- Mogor: Took Yurak's place as Prince Lotor's second-in-command. In the final episode of Golion, Sincline kills him.
- Commander Cossack: A replacement for Mogor, he was generally ineffective against Voltron, though like Yurak, he often went into battle throwing everything he could think of against the robot, including various robeasts given to him by Haggar for the purpose of battling Voltron. Calls himself "Cossack the Terrible".
- Queequeg and Lafitte: Exclusive to Voltron: The Third Dimension, she and her partner were drafted by Lotor for menial work. Lafitte was voiced by Tress MacNeille.
- Igor: A robotic figure who was commander of Lotor's army. Never seen after Lotor's conquest of the galactic administrative council.
- Ultra Droids: Planet Doom's footsoldiers.
- Karp : a cocky, egotistical ace pilot who is recruited by Lotor and Haggar. Although given a robeast to pilot, he retains his smug attitude by demanding that the robeast be painted red to match his trademark color. He wreaks considerable Havok on Arus and several other planets. He is made Governor General much to the annoyance of Mogor who disliked Karp's superior attitude. Karp was eventually defeated by Voltron; one of the few enemies that Voltron defeated by chance. Mogor was not disappointed that Karp had such a short career as Governor General. In the American Voltron, as was usual, Karp's death was covered by dialogue; in this case Lotor saying "Maybe he'll land safely and come again." Lotor's voiceover continues over what is actually a sunrise, however the added sound effect suggests an explosion on the planet. Lotor states that Karp, unfortunately did not make a very good landing and would probably be in no condition to fly for a long time.
- Skull Ships: One of the various attack ships of Planet Doom.
- "Mighty Robeast": When Zarkon and Throk joined forces, they created four Robeasts to combine with one of Lotor's ships to combat against the two Voltrons of the Lion and Vehicle teams. Armed with the Blazing Scimitar, the Blade of Doom.
- Rhino Beast: Rhinoceros-like Robeast, forms the main body and legs.
- Scorpio: Scorpion-like Robeast, forms the front body armor.
- Beetle: Beetle-like Robeast, forms the back and wings.
- Armor Beast: Armadillo-like Robeast, forms the arms.
- Lotor's Skull Ship: Forms the head.
- Dracotron: Evil counterparts to the lions based on dragons, the Dragons lived in an alternate dimension, but were so ferocious and destructive that they left it a desolate wasteland, forcing them to travel to other dimensions to steal food as well as structures within which to protect their eggs from their atmosphere. The most powerful Dragon is Black Draco, the black dragon. Five Dragons can merge to form Dracotron, an evil incarnation of Voltron with a superblast attack so strong, as indirectly stated in Third Dimension, that two blasts can destroy Voltron. In Third Dimension, the Dragons and Dracatron make multiple appearances and are destroyed each time, indicating that possibly any five Dragons can merge into a Dracotron.