A native of Kashyyyk, a young Kaarror was caught in the net of an unidentified slaver. Kaarror was taken to another planet in the hold of a ship. Kaarror became a gladiatorial slave, fighting with other slaves for the entertainment of the masters, and for the food and money he was given when he agreed to. As a slave, he traveled a lot in different starships.
During his travels, Kaarror knew an alien entrepreneur by the name of Phylus Mon. Phylus Mon had bet on Kaarror, winning an amount of money. Due to this, Phylus Mon felt sympathy towards Kaarror. In due time, when Kaarror was a two-meter adult, Phylus Mon bought the Wookiee's freedom.
However, probably at this point, Phylus Mon inserted an explosive near Kaarror's heart. The device would kill Kaarror should Phylus Mon die for any reason. The bomb could be deactivated if hit by an ion weapon, but Phylus Mon did not allow any ion weapon in his ship, the Animiasma. This mechanism was a security measure that Phylus Mon used in every one of his slaves. At the same time, Phylus Mon paid his slaves and insisted in calling them employees - but at the same time, all of them knew they could not leave Phylus Mon's service or they would die.
Suddenly free, Kaarror met a Wookiee criminal group, the Kalmec, and joined them, quickly rising through the organization. Like every other member of the Kalmec, Kaarror shaved his shoulders. As a Kalmec, Kaarror oversaw spice shipments through the galaxy. He found irony in seeing the rich beings destroyed by their own faults. Kaarror also worked in extortion, gambling and murder, defeating at least six Jedi and selling all of their lightsabers in the black market.
A galactic-level murderer, Kaarror was known for his uncontrollable rage, his sharp eyes and his skillful use of the vibro-ax.
Around 20 BBY, Phylus Mon called Kaarror with a job offer he could not refuse (Kaarror apparently knew of Phylus Mon's ruthlessness with deserters). Phylus Mon wanted Kaarror to go to the Cularin system along with some other of Phylus Mon's minions for an unspecified mission. Kaarror eagerly agreed because he did not want to be involved in the then-beginning Clone Wars.
Kaarror did not like the company Phylus Mon provided for the trip: A freaky-looking Spiner, a disgusting Human and specially a Wookiee-hating Trandoshan by the name of Gorak. The sneaky Barabel in the group was apparently a reputed bounty hunter working for Phylus Mon, so Kaarror decided to be respectful with him. Even although he wanted to trust Phylus Mon on the team choice, Kaarror could not trust the Trandoshan enough to let her stay behind his back. Similarly, Kaarror was mistrusted by the other team members.
Kaarror and the other minions attacked the Almas Sith fortress in Cularin system. The fortress entrance was being protected by six Jedi, but Phylus Mon sent no less than thirteen minions, including his Wampa bodyguard Ku-Kak. Phylus Mon's team killed four of the Jedi and defeated the other two, even although Gorak and Kaarror spent the whole battle insulting each other from different sides of the field.
In the fortress, Phylus Mon performed a Sith ritual to transform Kaarror and the others in Sith battlelords: After a dangerous, life-threatening process, they were supposed to rise as powerful military commanders that could use Force powers to deal with insubordination of their troops. However, something went wrong with the ritual: Kaarror and the other prospective Battlelords were stripped of their Force-essences, which would be stored in a large crystal.
Phylus Mon left the fortress with the crystal, but without Kaarror and the other empty bodies. Those bodies would then be found by a search team sent by the Jedi in the Almas Academy. The bodies were sent to the Academy. There, the Jedi tried their best to recover the lost essences and restore them to their previous state.
One player character in A Mon Alone can, at a certain point, enter this non-player character's body and use Kaarror's statistics until his essence can be freed (which means Kaarror's essence re-enters Kaarror's body and the PC's essence returns to the PC's unconscious body), or until Kaarror's body is killed in action. The text explains that some of the final scenes are so dangerous that they could easily kill the player characters - leading to the players getting angry.