Alien Enemy of My Enemy

HYGIEIA-AN OUTER RIM COLONY-IS DOOMED
The moon on which it was built hurtles toward an inevitable collision with the dead planet Hephaestus. The clock is ticking, yet when a distress signal arrives from a Weyland-Yutani biowarfare outpost, a desperate plan is launched to evacuate the trapped scientists. Meanwhile, across the galaxy a mysterious black substance rains down on Earth settlements, creating hideous monsters from indigenous creatures... and from human beings. Terran governments point the accusing finger at one another.
Thus on LV-846-a United Americas colony-high-level talks convene to address the galaxy-wide hostilities, but there's a Description brewing among the participants. One which could plunge the colonies into all-out war. The only hope for peace may lie with the deadliest ally imaginable...