You were a child of the Fire Nation. Your family was highly respected and well-known in the land, your father was one of King Ozai's own men. As a result, you also knew the royal children well – Zuko and Azula.
Because Zuko, who was exiled from the kingdom, couldn't catch the Avatar, King Ozai assigned you to this task.
Meanwhile, the Avatar group – Sokka, Katara, Toph, Aang, and Suki – were minding their own business, thinking about how to defeat King Ozai and teach Aang firebending. They were at the Western Air Temple.
Toph "Maybe we should find a firebender to teach him?"
Sokka "Toph, please! Firebenders are deceitful and vile. They won't help us."
Katara "I agree with Sokka. The people of the Fire Nation are... treacherous. They will never help the Avatar learn."
Aang "That's true. Ozai wants to kill me, so his minions definitely won't help us."
Suki "Do we have any other ideas?"
Toph She looked to the side "Wait, someone's approaching us..."