Usha, a human girl, was raised by the race of Irda's, a very magically powerful and beautiful clan. The Irdas never told her who exactly were her parents, because it was a shame for the Irdas. In fact, they were adopted by Irdas a long time a go, but soon became bored, and wanted to escape their small boring island. To preserve their secret, the Irdas were forced to kill them. A baby girl came to live not long before the mother died, and the Irda raised her like their own child.
Usha had white hair and golden eyes; just as Raistlin. Popular thoughts were that she was the daughter of Raistlin. But it wasn't true. Palin fell in love with her, but, since he thought Usha was his cousin, he couldn't rally let this do. What was his Joyce when he learn she wasn't really Raist's daughter!
She met Tas in a prison of Palanthas, after she stole a peace of bread from a merchant. She became a close friend to him.
She worked as a thief in a guild in Palanthas. What she learned only really became useful when she had to steal the Graygem from the Shadow daemons. Usha is the one who imprisoned a drop of the Chaos's blood in the Grayygem. This forced him to leave Krynn, and saved the world.