The Yuggians are an alien race that has since ancient times held colonies on Terra. They are a lifeform that is neither animal nor plant, described as resembling "fungal crustaceans", and consist of a strange kind of matter or ab-matter alien to our world that does not reflect visible light, but instead reflects EM wavelengths that are not recorded on ordinary film, perhaps thermal infrared, microwave or radar. In the Sol system, Yuggians live predominantly on a hidden planet not known to our contemporary cosmic maps, but they have colonies at least on Mars.