Kamala, a Kriosian empathic metamorph
An empathic metamorph is a creature perceived to be the "perfect mate" by changing its persona and behavior to meet another being's emotional requirements and sexual desires. It achieves this using a subtle form of telepathy which is more akin to empathy.
Kriosian empathic metamorphs, though random mutations, are relatively common. Males are the norm, while females appear once in every seven generations. As a result, such females are highly-prized as mates; they are forcibly adopted by the state from age four and put through a rigorous educational program to further increase their value as mates.
Kamala was a female Kriosian empathic metamorph that was given to Alrik to end the Valtese-Kriosian war. (TNG: "The Perfect Mate")