The Dust Plague is a species of spacetime-based organism that the Xeelee sometimes use as a weapon.
Dust Plague particles are very simple in structure. They are small knots of twisted spacetime, with no real distinguishing features.
The Dust Plague leaches the gravitational binding energy from objects it comes into contact with. Robbed of the energy holding them together, objects fed on in this way crumble to dust and gas. This phenomenon is the origin of the Plague's name.
The Xeelee unleashed the Dust Plague on the Solar System a few years after humanity escaped them by teleporting Earth into the Oort Cloud. The Dust Plague was used primarily to destroy the asteroid belt and eliminate any traces of human civilization and technology there, probably because the Xeelee no longer needed the Probes designed by the Paragons. The Xeelee eventually left for the center of the galaxy, allowing the Dust Plague to feed unsupervised.