Alien-kind

Of the 20-something empires to invade earth, some species of aliens have a greater relevance to the Somett Ridge base. Notably facehuggers provide a great inconvenience to the settlers, being relatively easy to kill but also enslaving the odd person. The galactic empire provides a more holistic threat, trying to quell any rebellion on the planet. The thing-style doppelgangers are kinda just slightly-murderous pests. Mantis aliens are known for their love and brutality.