Original sketch by Schnopszilla over on DA: http://fav.me/dbr1cps

Having lost control of the demon, the slimy, one-eyed, slug-plant monstrosity latched onto her hand with one of the long tentacles growing from what, for lack of a better term, had to be called its shoulders. With a searing pain, the lamprey mouth drilled into her hand, and its long, slimy tongue bored into her body. Shrieking, she grasped the tentacle to pry it loose, only for the monster to attach its second tendril to her chest.
Her body went slack, paralyzed by fear, and numbed by the sickly purple slime being secreted by the monster's body. Then the horrid sucking began. She could feel something ethereal, something vital to her very being, flowing out of her through the demon's tentacles. Her body began to melt, taking on the consistency of wet clay as it shriveled and shrank.
Meanwhile, the demon's slug-like lower body split into a pair of feminine legs. Its single eye became two, and the hideous, tendril shrouded mass that was its head slowly took on familiar facial features. They were her own.
Her own self now stood in front of her, still glistening as the last bits of purple slime were absorbed into the now human flesh. And she? She writhed on the ground as an amorphous blob with only the barest hints of her original features.
"Ah," said the demon, using her own voice. "This body will do nicely. Thank you for offering it to me."