Ghashiun was a member of a sandbendertribe who resided within the Si Wong Desert. He was the adolescent son of Sha-Mo and his late wife Yulduz. Ghashiun normally spent his days riding around the Si Wong on sand-sailers with his gang of friends, usually getting into trouble and stealing anything that was not well guarded.
Ghashiun had been somewhat adrift emotionally ever since his mother, Yulduz, died of skin cancer, a common affliction for people living in the sun-drenched Si Wong Desert. His relationship with his father was distant at best, and Ghashiun's lying and stealing only added to the schism between the two.
When Toph was preoccupied trying to keep Wan Shi Tong's Library from sinking with everyone else still inside, Ghashiun and others from his tribe arrived, seizing the opportunity to kidnap an unguarded Appa. After Appa proved to be too much to handle, he traded the bison to some merchants who were planning to take him to Ba Sing Se and sell him on the black market. As the sandbenders began to take off, Appa started shaking the merchants' transport trailer, to which Ghashiun mockingly replied that he was now the merchants' problem.
Ghashiun's tribe came to Team Avatar's rescue when they were being attacked by a swarm of buzzard wasps, scaring the flying creatures away. When Katara explained why they were traveling through their lands on a sand-sailer they had found, which, unbeknownst to them, had been stolen, Ghashiun was quick to scold her for accusing his people of theft while pointing out that they were the ones piloting a stolen sand-sailer. This argument caused Toph to recognize Ghashiun's voice, and she was quick to identify him as Appa's kidnapper. Aang furiously confronted Ghashiun, demanding that he tell them what he did with his bison. Ghashiun persisted in his innocence, but was forced to give up his act when Toph stated that he had ordered a muzzle to be put on Appa, Furious, Aang destroyed their sand-sailers and entered the Avatar State. Desperate to avoid being killed by the enraged Avatar, Ghashiun confessed his crime and offered to provide the group safe passage through the desert. The enraged Avatar did not react to this proposal, and Sokka urged the sandbenders to flee. Due to Katara's successful attempt at calming Aang down, Ghashiun and his tribe survived Aang's rampage.
Ghashiun was not a very kind young man, taking the belongings and possessions of others when they were not guarded. He also was not sympathetic, shown when he took off laughing at the merchants' problems with Appa. Aside from all of the stealing Ghashiun committed, he did have a small amount of heart, as he did offer to give Team Avatar safe travels through the desert after Aang triggered the Avatar State.