The first change came slowly, almost like the medallion was considering his request. When it did come, it came fast. Suddenly it felt as if his whole body was vibrating. He fell backwards onto the couch. His digits began separating, splitting in half so that each finger had another below it. His hands followed, then his forearm, almost as if he was lifting a new arm up out of his existing arm starting from the fingertips. A similar change was already progressing in his legs.
Blake was both thrilled and frightened. He was becoming two people, but he still didn't fully know what that meant.
His scalp began to tickle, usually a sign that his short-cropped hair was growing to a more feminine style. Reaching up with two of his four arms, he felt the longer hair, but also a crease that hadn't been there before. A strange sensation ran through him as his head split sideways down the middle, separating into two perfect heads growing on the same shoulders, the medallion draped down low around both necks. Blake realized he couldn't sense from the other head, nor did he have control over the second set of arms. He assumed the other head was asserting itself over its half of their strangely-shared body.
Meanwhile the other half of the changes progressed. While splitting a single body into two, the medallion was also busy transforming the two bodies into female forms. Already he was shorter, younger looking, more slender if you discounted the dual appendages. Breasts were forming, and his manood was slipping away.
Now, with just a common torso, he saw the second head moving forward into his field of vision. The split was pushing the second body and all its parts up on top of him, creating a new torso on top of the old. As the two torsos split, the top left behind breasts, then a taut tummy, and finally disjoined at the hip leaving two perfectly-formed young women.
Blake felt exhausted and more than a little sore. The weight of another body fully on his own didn't help, and with great effort he rolled with the new form onto their sides, slipped the medallion up over their heads, and turned the other so she lay face down, knees on the floor and head and arms on the couch cushion. The figure breathed heavily, seemingly as exhausted as Blake felt.
Too tired to worry about it now, Blake stumbled to her bedroom and collapsed on the bed. She was asleep before her head hit the pillow.