"Here's the thing, Astara" Dana's voice was almost kindly "You can't actually stop me." She raised her head to face Bara,whose face showed an expression combining terror, resentment and resignation. "My first crime, my betrayal of my oldest friend. Remember when I told you that someday Astara would slip up?"
Bara felt the special organ at the end of her tail wither and disappear. Her beautiful, crystalline horns were shrinking, and being reabsorbed into her skull. Her wings no longer gloriously reflected and refracted the ambient light, but grew dull and opaque, before crumbling into dust. The tail itself shrunk and disappeared into Bara's body. Her sharp, carnivore's teeth turned into the flat grinders of someone made to eat vegetables and grains. The two forks of her tongue painlessly joined.
"What's going on?" asked the changing demoness. "What are you doing to me? she screamed. Dana just smiled.
Bara's ears slid down from the top to the sides of her head, and reshaped themselves from feline triangles so something more rounded and hairless. Her face flattened. Her fur began to fall out, revealing a smooth skin underneath. Her claws popped out for the last time, then lost their edges and diamond-sharp points to become semitransparent nails. Her mammaries disappeared, her vagina closed up, and male genitals appeared between her legs as her interior was reshaped to match.
"Hello Barry" said Dana "Long time no see."