Plot
On the planet Morganthus, a monster kills the last survivor of a crashed spaceship. On the world of Xerxes, the Planet Master, someone whose face is obscured by an aura, instructs one of his military commanders to take the spaceship Quest to Morganthus. The Planet Master plays a chess-like game with an old woman, Mitri, who predicts that his actions will lead to ruin.
The Quest is piloted by Captain Trantor, a survivor of a space disaster that left her psychologically scarred. While approaching Morganthus's atmosphere, the ship veers out of control, but Trantor makes the landing. The rescue team then leaves the Quest in search of survivors.
The team reaches the other vessel and finds victims, making them think that a massacre took place. They take one body back for analysis and dispose of the rest. Cos, a young crewmember, becomes terrified of being on the ship. He is later killed by something that vanishes before anyone finds his remains.
The crew later discovers a force emanating from the pyramidal structure that pulled the Quest down and keeps it from lifting off. Leaving their ship, they approach the structure, which the psi-sensitive Alluma describes as "empty" and "dead". Splitting up, one team led by Commander Ilvar discovers an opening along a side of the pyramid. Ilvar insists, over the objections of his two younger counterparts, on going in first. While being lowered, Ilvar is attacked by tentacles within the chamber that drain his body of blood, killing him.
The other two continue on to the surface, linking up with the other group, and find another entrance. Leaving crewmember Quuhod to guard the entrance, the remaining four search inside the pyramid. Quuhod, who has a religious affinity for crystal stars, later sees one form in front of his eyes. Before he picks it up, the crystal springs to life and attacks him. As he tries remove it, a piece breaks off and begins sliding through his skin, forcing him to sever his arm to keep it from entering the remainder of his body. The dismembered arm becomes animated and throws the crystal star into his chest, killing him.
Alluma starts sensing something unusual, so technical chief Dameia is sent back to the entrance. Dameia discovers Quuhod's severed arm being swarmed by maggots. She blasts the arm and staggers off. One surviving maggot grows to giant size and, when Dameia returns to the chamber, proceeds to rape and kill her. On the ship, crewman Ranger sees Trantor running as if being attacked. Trantor combusts as she fires a weapon in an airlock. The remaining rescue team members find Dameia's naked remains, and return to the ship.
All the surviving Quest crewmembers return to the pyramid, where Baelon elects to stay behind and is torn apart by a monster. Inside the pyramid, Alluma, Ranger and Cabren are separated by moving walls. Ranger feels a rush of terror and before being attacked by a double. Regaining control of himself, he fends off the double, which fades away. Alluma, crawling through a tunnel, is attacked by tentacles which crush her head. Ranger and Specialist Cabren later discover that the planet creates monsters to attack people based upon their individual fears. Inside the pyramid, the two meet Kore, the ship's cook.
Cabren discovers that Kore is really the Master, who was masquerading as the cook on board the Quest. The pyramid is an ancient toy for the children of a long-extinct race, built to test their ability to control fear. Cabren is forced to confront the creatures which attacked the crew and also zombified versions of the victims, all of which he kills. After defeating his final challenge, Cabren "wins" the game. Kore starts dying, and the energy that engulfed his face engulfs Cabren. Stating that he will not play the game, Cabren decides to leave Morganthus. Kore's dying words express doubt that Cabren will manage to change his fate. Angered, Cabren kills Kore, but as the Master himself cannot die, he becomes the new Planet Master.
