She smiled an evil smile unlike he had ever seen before. Fangs sprouted out of canines. “What did you do, sexy?” she asked. Using her new strength she pushed Nathan back. She took her hands and began feeling over her naked body, she started orgasming again. Nathan removed Gene's cock and stood up, staring at her. He wasn't sure what he did but he liked it. He backed himself a step from the bed and looked down at his cock. He noticed it had black sex juices on it. “What?” He asked. He noticed some black cum oozing out of Katherine and onto her body. It crawled over and burrowed itself into her skin with a mind of its own. “Yea...” she said sexily. Her body contorted and slimmed, it got more muscular. Her butt grew strong muscle and her boobs pumped up at least one cup size. Her brunet hair darkened to a slick, straight black and her eyes curved outward. Her skin complected darkly and her fingernails grew.
“I'm creating a demon,” Nathan thought. At first he was scared but then he grew proud, “Haha! I'm growing a demon!” he exclaimed. Katherine stood and her back cracked. “Ha!” she said in pleasure, “this...this power...yes!” she exclaimed as her legs contorted. She turned around and he saw wings bud out of her shoulders. Small bat wings growing larger, her dark skin began to turn into a leather-like consistency as she crew to 6, no, 7 feet in length. A glow emanated from her head as the transformation completed. “Demonness” she whispered. “I am for you, Master Nathan, whatever you want it is my command.”
Hearing his name reminded Nathan he was still in Gene's body. He took a step, causing Nathan's real body to step out of Gene's. Gene lost the muscle mass Nathan's power gave him and dropped, passed out, on the ground. Nathan looked at him, smirked, then turned back around to Katherine.
“This medallion,” Nathan said, “there must be some purpose.” “Yes,” Katherine exclaimed, “to spread the evil darkness throughout the world.” Katherine answered. Nathan thought to himself that that wasn't much of a purpose, but he went ahead and played along anyway, all he wanted was to use his powers, he felt compelled and loved the effects. Perhaps that was all that mattered to him at this point. It seemed whatever he gave Katherine made her love it too.
Katherine leaped out of her window and flew away. Nathan communicated to her through his mind, she said she would return to human form and seduce a man so that she could spread the power of the medallion.