"Chosen Realm" is the twelfth episode from the third season of the science fiction television series Star Trek: Enterprise. It's the sixty-fourth episode of the series, first airing on January 14, 2004.
The episode begins with Commander Tucker and Ensign Mayweather gathering readings on a third sphere in the Delphic Expanse. Some time later, Enterprise receives a distress call from a Triannon ship which reports they have been damaged by a spatial anomaly. Enterprise takes them aboard, and D'Jamat, the leader of the group, has dinner with Captain Archer where he explains they have been on a year-long pilgrimage to a sphere. They believe deities, called the "Makers," constructed the spheres to transform the expanse, their “Chosen Realm,” into a paradise. D'Jamat then rejects T'Pol's scientific logic that there are only 59 known spheres.
Some time later, D'Jamat demands Archer turn over control of the ship or it will be destroyed, and demonstrates this by having one of his group self-detonate, killing one crew member. Having little choice, Archer submits. D'Jamat then sets a course for his home world and explains that he intends to use Enterprise to end a religious civil war that has embroiled his planet for a century. D'Jamat also examines the ships records and finds that Enterprise had extensive contact with the spheres--a severe violation under his faith. He then erases 19 XB of sphere data, and demands that Archer choose one crew member to die.
While Archer is contemplating his decision he approaches Yarrick, D'Jamat's deputy, questioning his resolve, but Yarrick rebuffs him. Archer then tells D'Jamat that he has selected himself to be killed, but requests it be done using a device they use for "waste disposal". That device turns out to be the transporter, which T'Pol uses to beam Archer elsewhere on the ship. Archer then contacts Doctor Phlox and they develop an airborne agent to neutralize the Triannon's organic explosives. Archer again confronts Yarrick and convinces him to help disperse the agent throughout the ship. Meanwhile, four ships from the "heretic" Triannon faction intercept Enterprise. During the fight, the crew manage to subdue D'Jamat and end the battle. In the brig, D'Jamat remains convinced his actions were justified, so Archer takes him down to the planet - which lies in ruins. The episode ends with the Triannons staring in horror at the completely devastated world.