Ylsa Henstak was a duergar merchant in Gracklstugh during the Rage of Demons[as of when?].
Ylsa was a rich merchant in Gracklstugh, notorious for leading caravans that always arrived on schedule. She was a member of the Merchant Council.
During the Rage of Demons, Ylsa was intrigued by how the local derro gained so much surface currency and jewelry.