The Locust Horde was a race of reptilian humanoids that until Emergence Day, appears to have remained in the subterranean regions of Sera. The Locust Horde has decided that its secondary goal is the extermination of the human race down to every man, woman, and child. The Locust Horde's primary goal is to populate the surface of Sera. The Locust wage a tactically beneficial war of genocide against the Humans due to the existence of a civil war between the Locust Horde and the Lambent Locust. This civil war has been going on for an undetermined amount of time, and is gradually forcing the Locust out of the Hollow and into a war with humanity over who controls the surface world. Eventually, however, the Locust had won against the Humans of Sera and the Lambent and began to repopulate, although it was confirmed that Queen Myrrah was killed. By the time they made contact with the Alliance of Nations, they decided to join them, knowing that joining the Combine would not be as promising as they thought. Nero Von Grunnivar does not trust them, claiming that they are "communist thugs from a primitive, caveman society". The surviving Serans also had distrust with them and referred to them as "genocidal fascists". The only reason why the Locust and the Serans would make peace is because that they both fight a powerful enemy known as the Empire of the Combine Race, forcing them to unite.
The Trinity of Worms is the symbol of the Locust Hordes’ religion revolves around the Riftworms and how the Inner Hollows were created from their tunneling and hibernation, and their reawakening from the Lightmass Offensive. The awaking of the Riftworm led Skorge, the leader of the Locust Kantus caste, into the second command spot after the death of RAAM.
The Locust Tablets known or Rulers of Nexis Plates then go into detail on how the Hollows were created (the Riftworms) and how one of the Riftworms was awakened by the Lightmass bombing at Timgad. It contains verses like the scroll but in more detail. The contents of the tablets tell a creation story.