Clockwork Sister

Aeon is a simulacra, a creation of flesh, clockwork and magic designed to protect their original humans from the deadly attacks of curse-workers.
She is an identical copy of her original, Mara, eighth princess of the Tamyin Empire, except for the brands and seals that mark her as artificial.
When Mara dies of natural causes, Aeon expects to be killed. After a botched attempt to euthanise her, she is taken in by a family of rogue simulacra living in the city slums.
When one of their number dies after injecting a dose of a serum that allows simulacra to change their bodies, Aeon is worried that someone is targeting rogues. A trail of discoveries unearths a deadly conspiracy, where friends and enemies are no longer what they seem.