Prince Lotor is the son of King Zarkon, the ruler of Planet Doom, and serves as the primary recurring antagonist in the series. As the prince of Planet Doom, he commands military forces and leads invasions against the planet Arus with the goal of conquering the galaxy. He is portrayed as handsome and physically imposing, with a ruthless and determined demeanor. Lotor is highly intelligent and sly, often devising cunning strategies to defeat the Voltron Force and achieve his ambitions. Despite his antagonistic role, his character is defined by a deep inner conflict regarding his father. He resents Zarkon and frequently plots to overthrow him, yet he also grudgingly respects his father's power and authority over the Drule empire.

A central element of Lotor's character is his obsessive infatuation with Princess Allura. He is determined to capture her and make her his queen, and this fixation often distracts him during battles, occasionally causing him to forfeit victory. In the original Japanese version of the source material, his obsession is rooted in Allura's resemblance to his mother, who was killed by his father, Emperor Daibazar, adding a layer of tragic motivation that the American adaptation largely removed. Over the course of the series, Lotor's role evolves from a loyal if resentful son to an active challenger of his father's rule. He eventually kills Zarkon and takes the throne for himself, becoming emperor of Planet Doom. He is later resurrected after being killed, returning to resume his quest for galactic domination and his pursuit of Allura.

Lotor is a skilled warrior and a capable military commander, leading fleets and personally participating in combat. He is also adept at manipulation and political scheming, traits that make him a persistent and dangerous threat to the Voltron Force. His key relationships are defined by his rivalry with his father, Zarkon, and his unrequited obsession with Princess Allura. These dynamics drive much of his development and motivations throughout the series.