The Koturians are a sapient humanoid species which modeled their civilization after Las Vegas, Earth. They are physically indistinguishable from Humans except for having hair of various different colors, such as green or lavender. Their homeworld is tremendously popular with alien tourists.
Once in a lifetime, each Koturian passes through a phase in which their bodies are capable of a complete transformation, both physical and intellectual, similar to a Time Lord's regeneration but even more sophisticated. This is conditioned by hormones and only happens when two Koturians are mutually in love. It is customary in their planet to arrange this transformation to occur during the wedding ceremony, using a special substance called the Imori Stone, which can trigger the process under the right emotional conditions by providing energy for the accelerated metabolism of the Koturians during their transformation.
- Something Borrowed, by Richelle Mead (2013)