Little is known of Arus' history. At some point, the Castle of Lions came to rest upon planet Arus with Allura and Coran in a deep sleep inside its cryo-pods, and the Black Lion locked inside its hangar. At some point, the Arusians came to worship and believe in the existence of the "Lion Goddess" as told by "the ancients", and carved symbols of the goddess around the Castle. The Castleship and its occupants are awakened once Lance, Shiro, Keith, Hunk, and Pidge arrive in the Blue Lion. The local Arusians soon send Klaizap to investigate the Castle after witnessing Voltron battle Sendak's warship.
Arus is a hospitable planet full of water, green plant life, and a safely breathable atmosphere. It seems to have a moon larger in size compared to Earth's moon, noted that it could be closer in distance to its moon as well. Though Earth and Arus share a lot in common, both are tremendously far away from each other. According to Shiro, Arus' location is in an unknown sector of the universe full of unfamiliar constellations.
- Local Arusians never ventured inside the Castle while it remained dormant.
- Arus is the first planet under Voltron's protection and alliance.
- Local Arusians believe Allura is the legendary "Lion Goddess" and Voltron the "Mighty Robotic Angel" sent to destroy them.