The Order of Leviathan
A thick belt of debris encircles the planet, a result of Typhon’s escape from his imprisonment in the moon. Much of this debris is in unstable orbit and enters the atmosphere in large meteor showers. Many of these chunks are large enough to not completely burn up, and actually manage to impact the surface. Petronius Varius was killed while investigating such an event. (see Tracking Petronius)
There are some reports of this debris bringing evil and monstrous beings down with it when it falls to earth. Arcturus Leto told the party that he believes the egg recovered by Doctor Aein Belwhether the Opaque may have such an origin. That creature died before much else could be learned, however.