History
Some time in the past, Lotor was born as the son of Zarkon and Honerva, an Altean alchemist. He became exiled for unknown reasons. The prince does not return to the Empire until Zarkon's obsession with the Black Lion leads to the emperor's defeat at the hands of the Voltron team and their allies, putting Zarkon in a comatose state under the care of Haggar. The exiled prince is summoned by the witch to lead in his father's stead.
Prior to his return to the Empire, Lotor took in Acxa, Ezor, Narti, and Zethrid - all half-Galran women - as his top generals. He also became known for allowing planets he conquered to rule themselves and for fighting alongside his armies like a lowly private - things many in the Empire regard with disgust.
Season Three
The Galra Empire is brimming with treachery by the time Lotor arrives. Distrustful of Haggar for the witch's refusal to let anyone speak or see Zarkon, Throk plans to usurp the throne with backing from the generals in his sector and asks for more assistance from another Galra commander at the Empire's gladiator arena, where the audience is filled with military personnel gathered to watch a small masked warrior battle a massive beast.
Unbenkownst to Throk, Ezor and the other generals of Lotor's royal guard sit hidden in the audience around him, listening and relaying the conversation to Lotor himself - the very warrior Throk is watching fight. When the beast is defeated, Lotor removes his helmet to reveal his identity and publicly calls out Throk's treachery to the audience, offering to accept the commander's challenge for the throne through honorable combat. With his plans exposed, the pressure of the audience upon him, and the royal generals blocking his escape, Throk agrees to the duel.
After a ferocious fight, Lotor stands the victor and Throk waits to be slain, but the prince spares his life, giving a rousing speech to the audience about inspiring loyalty in their conquered foes instead of fear. His speech wins over the support of the Empire's military and that of Throk, who pledges his loyalty. Soon after, Lotor meets with his generals and orders them to transfer Throk to the far reaches of the Empire to rot.
Lotor's next move is to travel to planet Puig that has just been freed from the Galra Empire's control by Team Voltron and left unguarded. His generals are able to overpower the defenseless people without casualties, and Lotor personally offers their leader a chance to join the "new" Galra Empire, claiming they will never need Voltron's so-called protection again. He leaves Puig to study the movements of the Voltron Lions on his Royal Warship, intrigued that there have been no recent sightings of the Black Lion, speculating it means that Voltron is unable to be formed. He sends Narti to Puig, who uses her mind-control powers to control the Puigan leader, sending a false call for help to Team Voltron to lure them to his location.
The prince is not aware that Keith has suddenly become the new Paladin of the Black Lion because of Shiro's mysterious disappearance. When the Voltron team arrives, Keith, Hunk, and Pidge are the only Paladins able to leave the Castle of Lions in a Lion, as the Blue Lion refuses to respond to Lance. Lotor greets the three Paladins outside of Puig from his Royal Warship, declaring himself the son of Zarkon and Emperor Pro Tem of the Galra Empire.
His fleet of fighter jets proves a worthy match for the three Paladins to handle, but Lotor is calmly nonchalant that the Black Lion is functioning and wonders about the two missing Lions. With more fighters launched to force the Paladins into a desperate situation, Lance is soon chosen by the Red Lion for his matured heart and acceptance of Keith as the new leader; he enters the battle to assist the other three Paladins, but with little handling of his new Lion.
The team's disarrayed display means Lotor notices that the Black Lion's pilot is not in full control. After the Royal Warship's ion cannon deliberately blasts the Black Lion and the Castle of Lions, Lotor's probing bears fruit: Allura arrives in the Blue Lion, newly chosen as its Paladin. With the truth revealed that all Voltron Lions are functioning, Lotor believes he has witnessed enough and retreats with his fleet instead of continuing the fight.