[Ideas...]
Falling through a doorway to another world, Amber Grant soon after finds a small glowing chunk of metal. It is about the size of an apple slice and turns to fluid in her palm. She hears a voice and, in her mind, sees a woman who, with her huge bust and clawed feet, is definitely part-bird. The tall, hourglass-shaped woman implores her to accept the challenge the fragment presents.
What challenge is that?
The right to rule. Find the other fragments of my collar and you can be Empress of the galaxy!
Sure she is just dreaming, Amber agrees to play along and is transformed by liquid metal as it glides over her skin to form an eye on her chest. The young woman can feel a power flowing into her from the fragment, sparks crackle around her fingertips, then her bust begins to expand, doubling in size before she lets off a nova of energy. When she can see again, her body has changed.
Now a candidate for Empress of Ul'Naji, Amber has become helplessly embroiled the galactic power struggle. Multiple factions vie for control of the sprawling Ul'Naji Empire. She is attacked, almost at once, by the faction lead by Bhilith, another Empress candidate, and she is saved by a faction of Asari-like aliens--who are pretty much mono-sexed with the primary dimorphism being bust versus butt.