Impaz is the only remaining inhabitant of the Hidden Village of Twilight Princess. Impaz is often theorized as being one of the mysterious Sheikans due to her location and traits. The Hidden Village is also hinted at being the old Kakariko Village from Ocarina of Time which was founded by the Sheikans, further supporting this theory.
In Twilight Princess, Impaz plays a key part in helping Link understand the power of the Dominion Rod. For more information on Impaz, check out the Zelda Wiki