Princess Allura was born and lived on Altea along with her mother, her father, King Alfor, and their royal advisor, Coran. During her father's life, the Alteans held an alliance with the Galrans. King Alfor built the Black Lion from the material found in a comet that collided with Zarkon's planet, and Zarkon became the Black Paladin. The origins and creation of the other Lions of Voltron is unknown, but Coran's grandfather built the Castle of Lions to house them. However, Zarkon sought to have the power of Voltron for himself so he betrayed Alfor and the Alteans, mercilessly attacking them with the might of Galra fleets. This led King Alfor to put Allura and Coran in a deep sleep inside cryo-pods within the Castle of Lions, and to scatter the Voltron Lions to hidden locations across the universe so they would not fall into Zarkon's hands. Alfor met his end by unknown means, and the Altean race was destroyed along with Altea and its entire solar system.
Altea was a planet blooming with the beauty of its purple juniberry flowers. The Altean race built a civilization with impressive technology seemingly unexplainable by science alone. Altea seemed to have several artificial megastructural rings encircling it, all equally separated from each other. It is unclear whether Altea's blue-colored surface was its diffraction of its atmosphere due to their star or that most of Altea was covered with oceans. Coran does not recognize the concept of rain, but claims that boiling hot rocks frequently fell from the sky.
The race of people native to Altea are called Alteans. They are aliens nearly identical to humans of Earth. Defining Altean features are pointed ears and sickle-shaped markings on each cheekbone, as well as pupils with a colored speck in the center. Altean males have been seen with blue facial markings, while Allura, the only known female Altean pureblood, has pink markings. The royal family is known to have a trait of white hair in its bloodline. Haggar is described as being Altean by Allura, but it is not known if she suffers an altered appearance by unknown means or if she is an Altean hybrid.
The culture of Alteans remains largely unknown, but they appeared to be a morally-straight, well-intentioned race that valued diplomacy, protection of allies, and peace. Their currency was called "groggeries" which came in the form of Altean crown bills and was used by more races than their own. The groggery was named after "King Groggery the Infirm" and had his face printed on the bills.
Alteans are shown to have a long lifespan; Coran explains that the Castle of Lions is 10,600 years old by the time the human Paladins arrive on Arus, and states he was alive at the time his grandfather was building the Castleship. This places Coran's age around 600 years old at the very least. He is considered "later in life" or old for an Altean.
Altean energy is used to power teludav devices built with scaultrite and create wormholes for spacecrafts to traverse vast distances of space, but only a few Alteans were capable of this feat; the only living Altean known with this ability is Allura. Altean energy also has immense healing properties and was once used by designated "Sacred Alteans" to restore Balmera in a rejuvenation ceremony after Power Crystals were extracted from the living planets to provide a mutually beneficial relationship; King Alfor was one of these Sacred Alteans. Allura's energy allows her to restore a dying Balmera simply by contact. Her energy has manifested itself as defensive and offensive magic as well. It is unclear if her abilities are because of her royal bloodline, or would be possible for other Alteans.
- Having rocks as rain could be referencing models of exoplanet "Vaporized rock showers".
- Alteans can suffer from a harmless condition known as "the slipperies", where their bodies excrete extremely slick fluid to such an extent that walking is nearly impossible, as the Altean will likely slip, fall, and slide instead. The condition is common for Alteans of older age and usually only lasts a couple of days.
- "Sloven-day-ho" is Altean for "gone".