We dont know what they are…
Most scientists believe they’re a mutated version of Sera’s native life forms. A minority claim they are aliens. Ask any Gear and they’ll tell you the Locust come straight from hell.
We know they live underground. How and exactly whereare impossible to determine, however, because the cavern systems in Sera’s mantle are, for all practical purposes, endless. As a result of swelling in perpetual darkness, they have an aversion to light … one of our few advantages. All attempts at negotiating with the Locust have failed, and all overtures of peace have ben answered with violence. The only conclusion we can draw from their actions is that they want every last man, woman, and child dead.