Leah was the ward of Deckard Cain and the biological daughter of Adria and Aidan/Diablo

From the outset, Leah was conceived as a host for Diablo. While the three Prime Evils had masterminded their exile to Sanctuary, Diablo had taken the plan one step farther. He would become the Prime Evil, combining the essences of the Great Evils into a single form. And to do that, he would need a vessel to inhabit.

Leah grew up to be an ally of the Nephalem

Leah has immense power from her heritage she can’t control and she’s a skilled archer

Leah has dreams to be an innkeeper one day

Leah as of now is reading ancient texts and reviewing her Uncle’s writings in order to help the Nephalem and Tyrael stop the great evils