The Dragon Mistress was the title attributed to the sand dragon that acted as the protector of Hethrir's headquarters on his personal Worldcraft.
In the year 14 ABY, Jacen Solo, who was only five years old at the time, employed his developing Force powers to converse with the Dragon Mistress and convince her to transport him, his sister, and all the other captured children away from the pursuing Proctors.
The children were compelled to abandon her, given that the path required for their escape from the base was insufficiently wide for her large size. As the children proceeded further, Jacen held onto the hope for her well-being, as their final auditory memory of her involved a loud roar, implying that she was engaging in combat with the proctors in pursuit.