The Cruixers were a fairly widespread plague in the galaxy; they were basically space worms, but they were aggressive and territorial. How they had spread throughout the galaxy was unknown, and although their physical characteristics were different from environment to environment, the genetic tests carried out In all the years of space exploration were clear: all of them, despite small genetic alterations, belonged to a common branch.
Normally, the worms remained inside the planets and asteroids, corroding them from within with their tunnels, although they did not really feed on rocks, but on the microorganisms that were inside the earth. When they sensed or detected organic life, they attacked without mercy.