Rachel is a beautiful woman who at first glance seems entirely normal. However, she cannot tolerate the touch of sunlight, and possesses the ability to transform herself, or parts of herself, into an animate mist of such subtlety that it can even pass through solid objects unimpeded. She can also use this ability as a form of attack, by dematerialising then rematerialising herself inside another person's body.
The other 'Breed look down on Rachel's physical perfection with something akin to pity; behind her back they call her "The Hostage," although whether this is a reference to love or beauty is a matter nobody will discuss.
Rachel was the first of the Tribes of the Moon to meet Lori when the latter came looking for Boone in Midian. She befriended Lori after Lori saved her daughter Babette, who had been caught outdoors in the sunlight.
Later, after Boone (now one of the Nightbreed named Cabal) was incarcerated by the zealous Shere Neck police, Rachel was instrumental in Boone's rescue, using her abilities to break through into the cells and kill one of the officers guarding Cabal.
Rachel made it back to Midian in time to witness the destruction of the city at the hands of the xenocidal Sons of the Free, although she and several others escaped to safety after Cabal unleashed the Berserkers.
Rachel has a daughter, Babette, and although Babette's abilities seem quite different to her mothers, it is possible that her powers have yet to mature.