Great. It's gonna be another one of those planets."
- ―Warthog, upon seeing an Aleena flying a can-cell over Aleen
A world with a desert-like surface, Aleen was unique in that it contained a series of complex caverns in the upper crust that was viewed as a second biosphere with its own unique atmosphere. Formed by the growth of the unique arbozoic trees, the caverns were also comprised of tunnels carved by water, lava, and tectonic sheering. Maintaining a unique climate and an atmosphere dangerous to the surface-dwelling Aleena, the planet's two sentient species made the conscious decision to recognize the divide between the two environs and remain separated. Aleen's surface was dotted with the remnants of Aleena colossi that stood as relics of their ancient society abandoned in favor of a simpler lifestyle.
The homeworld of both the Aleena and the Kindalo species, Aleen was a world of two distinct environs that had a shared, yet separate history. Establishing a strong culture and a fierce army, the Aleena built towering monoliths that were vital to the religious orders that formed on the planet in the earliest days of the Galactic Republic, and long before the galactic community had discovered the world. Undergoing an expansionist era, the Aleena settled other worlds and spread out into the greater galaxy. The Aleena came into conflict with the Kindalo that lived beneath the surface of the world, and the two cultures waged a terrible war that caused great damage to both societies through the use of technological weapons. When the causalities grew to such heights as to threaten the existence of life on Aleen, a compact was formed that secured the notion that neither society would interfere with the other again. To this end, the Great Seal was forged to serve as a reminder of the compact, and was placed within a primary tunnel opening that allowed access to the Underworld.
While the Great Seal was more symbolic then any actual barrier to the Underworld, as multiple tunnels and caverns were spread throughout the upper crust of the planet, it was a revered site among the Aleena. Vowing to leave behind the society that caused the near apocalypse on Aleen, the Aleena entered into an era of self-imposed seclusion and scaled back development considerable. Forming into kinship clades known as tahikos, the individual settlements maintained contact with a planetary government that advised the King of Aleen. Over the course of the millennia, Duros spacers discovered Aleen and eventually introduced the Jedi Order to the world. Establishing a chapter house over top of the Great Seal, the Jedi protected the world for a time, before abandoning their chapter house and allowing it to fall into disrepair.
While the Republic saw operations on the world during the Clone Wars when the Great Seal became dislodged and the two atmospheres began to intermix and groundquakes began to cause major disruption on the planet, their work was humanitarian in nature. During the relief effort, a mysterious being called Orphne was recorded by Republic agents, though her nature remained ambiguous. When the Galactic Empire came to power at the end of the war, the Empire established a observation post on the moon of Trohlu.
- Star Wars: The Clone Wars – "Mercy Mission" (First appearance)
- Star Wars: The Clone Wars – "Nomad Droids" (Appears in flashback(s))