Ehlastra

She can be found chained next to the bed of of the Fire Giant  in Yaga-Shura's Lair.

Gameplay
She gives you here name when you first talk to her.

Quote: "My name is Ehlastra, a warrior from the northern lands. I had heard legends of Yaga-Shura, a child of Bhaal born unto a giantess. I came to this place to see if the legends were true."

The berserker came from the north to join Yaga-Shura but ended enslaved as his concubine. When you free her, you receive XP and information about Yaga-Shura's Heart and Nyalee's heart.

Extension
When you free her, a mod provides an option to let her join your party. She is a lawful-evil berserker who can accompany you until the ToB final battle (BG2EE or EET only)..