The Lurker in the Angles is an alien entity from another universe. It was released during Mission 21, presumably by Dr. Maurice Sanctor. He and Morul raced to see who would get to be possessed by the alien entity. Ultimately, Morul won the race, and was taken over completely.
After a few failed attempts to stop the Lurker, it partially destroyed the anomaly that contained it and the team. This allowed the team's survivors to escape and report the situation to Steve. Steve promptly crashed a spaceship into the planet, and caused a massive automanipulator overload. This wasn't enough to stop the Lurker, and now it is spreading its influence over our universe.