The Arn are an extinct avian race and creators of the Hork-Bajir.
The Arn were an avian race that originally inhabited the Hork-Bajir homeworld. They are quadrupeds with short wings, and two enlongated arms ending in claws. Their are bodies are covered in brightly colored feathers vary wildly in shades. Their faces are dominated by glittering eyes and small, red mouths.
The Arn civilization arose from a world that the Andalites refer as Sector 5, RG-21578-4. The Arn mastered the sciences of biological innovation, neglecting interests in interstellar travel.
At some point in their history, Arn detected an asteroid would collide with the world and sought to develop spacecraft to escape the impending doom, only managing to relocate some of their people to the nearby moons.
After the asteroid collided with their world and destroyed much of the life of their planet, the surviving Arn found themselves in a new world in which the environment precarious and the balance of life was hanging by a thread within small valley. To remedy this they created an entirely new ecosystem composed of giant trees to keep the planet alive and stabilize the atmosphere.
To maintain the health of the trees they created a race race biologically driven to ensure their survival: the Hork-Bajir.. The Arn then decided to shield themselves from any more such catastrophes by moving their settlements into the deep chasms caused by the disaster. To keep their isolationism intact the Arn also created the creatures of The Deep to ensure that their creations would not stumble on any of the Arn settlements deep in the planet's chasms.
The existence of the Arn was discovered by Aldrea and Dak Hamee who led the Hork-Bajir resistance group against the occupying Yeerks. The Arn were eventually discovered by the Yeerks. The Arn believed they had no fear of the Yeerks as they genetically modifed themselves to be unsuitable hosts, but the Yeerks instead choose to enslave the Arn as a cheap labor force to mine metals and at other time target practice.
When the Andalite task force arrived at the war, only one Arn settlement remained free. The Arn conspired with War Prince Alloran to develop a virus that would wipe out the Hork-Bajir and free their world from the Yeerks. However the plan was discovered by Aldrea and Dak who sought to prevent a genocide. In the end the virus was released which decreased the Hork-Bajir population to thousands from millions, preventing the Yeerks from enjoying the full fruits of their victory.
Only one Arn survived the Holocaust, Quafijinivon who eventually learned that a free Hork-Bajir colony existed on Earth after eavesdropping on Yeerk transmission chatter. He risked everything to steal a Yeerk ship and traveled to Earth and eventually discovered the colony on his own. He offered the Hork-Bajir a chance to reclaim their world and for him to achieve his revenge against the Yeerks. He wished to create a new colony on his world, by collecting DNA samples of the Hork-Bajir in the colony and lead a resistance movement on the Hork-Bajir Homeworld.
The Arn were masters of genetic engineering, creating life through intricate design and purpose. The Arn possessed technology that allowed them to track their creations and also control the various monsters they created using chips implanted in their heads, which allowed them to give the creatures simple commands. The possessed the ability to store a person's personality and revive them using a device called a ixcila using a host that was the mental opposite of the personality.
- Animorphs: Hork-Bajir Chronicles