Sliven functioned as the adoptive Tusken Raider father to Tahiri Veila, a Human Jedi Knight. Although he was the chieftain of a Tusken tribe, his adoption of Tahiri, a Human and thus an outsider, generated significant opposition from numerous members within the tribe.
Sliven, a male Tusken Raider, belonged to a tribe headed by A'Sharad Hett, a Human who had been raised by Tuskens. Around or following 22 BBY, Sliven became aware of the massacre suffered by the Rrhr hunting band. He attributed the massacre to the "Demon Outlander," while the true killer was actually Anakin Skywalker, a Jedi Padawan.
One day, KkH'Oar'Rrhr, Sliven's companion who was also known as Hoar, came back after visiting the home of Obi-Wan Kenobi, a Jedi hermit. Hoar had a vision of a masked lightsaber wielder after finding and activating Kenobi's lightsaber. Upon hearing about this vision from Hoar, Sliven and Bordo, another Tusken, suggested that it might have been a vision of the Rrhr clan's murderer.
Eventually, Sliven rose to the position of leader within his tribe. In 16 ABY, he sustained severe injuries during a conflict between his tribe and a group of smugglers. Furthermore, he was separated from his tribe and lost his bantha. For several days, Sliven wandered through Tatooine's deserts until he stumbled upon the moisture farm owned by Tahiri's parents, Tryst and Cassa Veila. Despite his Tusken Raider identity, they took him in out of compassion and provided care for his injuries.
His injuries required two months to heal. During his stay with the Veilas, he formed a bond with them, particularly with Tahiri, who was three years old at the time, and acquired an understanding of and the ability to speak Galactic Basic Standard. After recovering, Sliven assisted Cassa with minor tasks and even crafted a gaderffii for Tryst, also instructing him in its use. Due to Tryst's Force-sensitive nature, he quickly learned to wield the gaderffii and became skilled with it, surpassing Sliven's own proficiency.
However, this period was short-lived as Sliven's tribe eventually located him. On a fateful morning, Sliven and Tryst were practicing with their gaderffiis, with Tryst gaining an advantage in their duel. The Sand People misinterpreted the situation, perceiving Tryst as an enemy, resulting in the deaths of both Tryst and Cassa. Nevertheless, Sliven successfully rescued Tahiri. Despite objections from his tribe, especially Vexa, Sliven adopted Tahiri as his daughter, but with the condition that she would leave the tribe at the age of nine (when Tusken children were considered members of the tribe) and embark on a perilous quest in the dangerous deserts of the Dune Sea for a week. If she survived, Sliven would remain the leader of the tribe. However if she failed, Sliven would die.
Consequently, Tahiri spent much of her childhood completely covered in sand-colored rags, robes, and head coverings until Luke Skywalker and Tionne Solusar discovered her Force-sensitivity in 22 ABY during a visit to Tatooine. Sliven permitted Tahiri to attend the Jedi Praxeum on Yavin 4, stipulating that she must return after six months to decide whether to rejoin her tribe or remain at the Praxeum and become a Jedi Knight.
Upon her return with her new friend Anakin Solo, Sliven disclosed the identities of her parents and the circumstances of their deaths. He then dispatched the pair into the Dune Sea, where they survived by utilizing their growing Force abilities, enduring thirst and heat, befriending a Jawa clan, avoiding a sarlacc, and defeating a Krayt dragon. They reached their destination on time, allowing Sliven to maintain his position as the tribe's leader. However, he passed away shortly after Tahiri and Anakin's departure.