The Demis, or Los Demonios, are a group of aliens, who are at war with The Hosts. In Disposable Heroes, this alien have attacked two Outliers. In Bonzo, Everett Kynes sees the footage of the Demi attacking the Outliers. Later, he came to speak with the Demi, who is being held captive. They also destroyed The Factory to prevent the Hosts from using their defense weapons.
Before the Arrival, these group of Demis have attacked The Hosts' homeworld and driven them off their planet, forcing the Hosts to flee to Earth, which led to the occupation of humanity's home planet.