Naga

An alien race who looks similar to Lamia but can change form at will. They can change into the snake species they are or into an Elf. After millennium of wars their planet has become unable to support life anymore. They now live in small biospheres scattered around the planet and travel between them is limited. The population has been decreasing over the years due to the low birthrates of males. Any male Nagas are treated as royalty and taken from their parents immediately. They have explored the nearby planet and used some males they had found as genetic material for expanding their population. After living like this for years they decided to move their dwindling population to a nearby planet that has similar people living on it.After 25 years they have finally finished construction on a floating island they can populate.