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Monsters
She ran forward, letting the cool breeze pass over her. The thrill of it all was exhilarating: the burning of the muscles, the damp warmth of the sweat on her body and coated her lithe, curvaceous form. Her senses sharpened as she inhaled a pungent odor in the air; she rapidly shot a glance behind her and saw the monster. She panicked, and began to run faster, legs pounding into the damp soil and hair flowing in the wake of air behind her. But, the monster kept pace with her. It called out in a strange tongue she couldn't understand, and it sounded as if it was pleading with her.
No, she told herself, I won't let it get me. I'm free now, and that is all that matters.
She forced her tired legs to move even faster, and they did. The mere thought that she might have to fight seemed to invigorate her, and she felt her new sharp senses become even sharper. She pulled off the clothes the monster had forced her to wear, so she could run faster.
She kept running, and it kept calling. The monster called even louder, but she refused to listen to its sweet voice of lies and bondage. She stole a glance over her shoulder, and realized it was tiring out. She steeled herself to attack it at its weakest, spun around quickly, and launched herself toward the monster. She connected squarely with its chest, and they both collided into the ground with a bone crunching thud.
As she got up, she smelled its blood. She knew now what she had to do. Not bothering to even look into its deep, dark eyes, she began to rip it to pieces. She tore into the monster with her claws, and took a bite out of it throat, allowing the warm blood to run down her face. But, as she came back up, she saw its face; something snapped in her mind. She pushed herself up and stumbled backwards, looking in horror at her clawed hands, covered in the blood of her fiancé.
She backed up rapidly, stammering to herself, "Wh-what happened?" All that came out, though, was a feline hiss. They had been so happy together, what had happened. Then she remembered the cat that had appeared and had taken them to this desert, with its glowing red suns and dark desires. She had been human then, but something changed. She remembered being thrilled when her anger and frustration had seemingly given her heightened senses, and then she remembered her fiancé begging her to stop giving in, that she was changing, that they had to get away from this place. But she hadn't listened, and had fled. She liked her new-found senses and feline body, with its supple muscles and beautiful form. She enjoyed the thrill of the hunt. And above all, she enjoyed being able to run free across the open land, chasing the scent of new prey and fresh meat.
As she recoiled in horror from his body, she felt herself slipping, losing her control. In fact, she thought as she stalked back toward the body on the ground, why was I even worried. It is the law of the jungle, after all, that only those strong enough survive, and he was obviously weak. He… It tried to put me in bondage again, take away my freedom. A hungry look gleamed in her eyes, and she pounced upon the monster's still form and chomped into his fresh carcass. She tore off a hunk, flinging blood through the air, and howled at the sky. From all around her, her new found sisters and brothers answered her howl. Her last cognizant thought, before she slipped into the oblivion of feral instincts and animal urges, was a question – Who was the real monster?
This is set on the Cheetah Planet, from Doctor Who: Survival