Aleen Minor/Legends

Aleen was the rocky, temperate homeworld of the Aleena, located in the Inner Rim Territories. The Aleen Classic, a popular podracing event, was held annually on the planet. Famous Aleena podracer Ratts Tyerell was a native of Aleen. Its also notable for being the homeworld of the Aleena Jedi Master, Kazdan Paratus

History
The inhabitants of Aleen lived both above and beneath the planet's surface. Above ground lived the peaceful Aleena for whom the planet was named. Beneath the surface dwelled the tree-like Kindalo and the mystical being, Orphne. Air became naturally filtered as it fell through the ground, to the point that it was breathable by the Kindalo. Unfiltered surface air poisoned the Kindalo. Likewise, filtered subterranean air was poisonous to the surface dwellers.

Aleen was iscovered by Galactic Republic scouts during the Great Manifest Period. Granted direct representation in the Galactic Senate; the world was represented by Senator Bogg Tyrell during the waning days of the Republic.

Over the years aligned with the Senate, the world welcomed the construction of a chapter house of the Jedi Order. The world was known to have produced at least two Jedi Masters, Tsui Choi and Kazdan Paratus, who both served during the Clone Wars. Around 21 BBY, the planet began suffering from groundquakes caused by the Kindalo because the seal had been opened under mysterious circumstances. The Kindalo thought the Aleena were responsible and so caused massive groundquakes in retaliation prompting the Galactic Republic to send a squad of clones led by Wolffe also accompanied by C-3PO and R2-D2 for translation, to undergo a relief mission. There, the droids discovered the Underworld and were able to seal the breach and restoring peace. Although the clones were skeptical, the Aleena were overjoyed.

Behind the scenes
Due to the discrepancies between the previous sources and the planet described in The Clone Wars TV series, Jason Fry stated that those Aleen are two different worlds. The old Aleen is Aleen Minor and the new is Aleen. This was later formalized in the The Essential Atlas Online Companion.