Sienna was covered in a thin layer a glossy sweat and hung from the ankle chains completely exhausted and barely able to move. The relentless machine inside her had changed tunes and now was a slow mind-numbing rumble just barely audible in the cool workshop air.
Darlene had been writhing in pleasure as the evil fog swirled and moved around her body, but now stood staring at Sienna with an wicked smile of victory, "You will submit to the dark master eventually my sweet Sienna. Already I feel him penetrating your desires and sealing the deal with your body. Once you replace my debt, I will be free from this place and you will be trapped instead."
Sienna moaned and twisted as the wispy fog of the evil demon wrapped around her helpless body. The vibrations of the device inside her came bursting back to life with a vengeance and she screamed behind the massive red ball in her mouth, "Ahhhhhhh! Mmmmmppppphhhhhhhhh....Mpppppppphhhhhhhh!" After another orgasm, she jerked and swayed around in a circle and tried to breathe deeply in through her nose because the gag kept her from taking a deep breath otherwise. As she did, the swirling fog rushed into Sienna with each of her hurried breaths. After a few moments, Sienna calmed and her eyes popped open. They were glowing.
Darlene cried out, "Yes! It worked! Now I am free and you are the slave to the Master. You were weaker than I thought. It took me days to give in, and you barely took ten hours to sell your soul. Lucky me." She was strutting around Sienna poking and laughing when she heard a rumble in the room.
The floor in front of Sienna glowed red and a large red sigil glowed as fog poured up onto the floor. Slowly a large block of marble or granite rose up through the fog. It was black and smooth with patches of lighter colors in random patterns. As she watched, the floor became solid again, the fog vanished and the sigil faded, then the strange block morphed on the top. A tendril stretched out of the center and reached into the air and began to form into a chain. One the end a heavy metal collar began to take shape.