The Machine

Near the center of the Galaxy, the Machine was a planet-sized construct of terrifying power, hurling entire star systems into a supermassive black hole.

History and specifics
The Traveler, Wesley Crusher, witnessed the Machine destroying star systems, including inhabited ones, by casting them into the black hole named Abbadon. Wesley contacted the Travellers for help but they had fled, having had many frightening encounters with the Machine in the past. Wesley contacted his old friends aboard the Federation starship USS Enterprise (NCC-1701-E) for help.

Wesley transported the Enterprise to Abbadon where Worf led an away team inside. Chen recognized the Machine as the product of the same Machine Race who constructed V'Ger, while Taurik downloaded information on the Machine's mission. They learned it intended to build Abbadon to a large enough size and crash it into Sagittarius A*, creating a wormhole and causing a shockwave that will destroy all lifeforms in the galaxy over the course of several thousand years and instantly eradicate all subspace, destroying technology and faster-than-light travel and communications.

Data communicated with the Machine, which judged the Fellowship of Artificial Intelligences unworthy, and the Machine begins plunging the sentient ship Altanexa into Abbadon. Most of the Fellowship evacuated and Data, along with Gatt, tries to retrieve two escape pods containing Akharin and Rhea. Data, faced an impossible choice, to save Akharin (the only one who could restore Lal) or Rhea, who had just agreed to come away with him and help him raise Lal. Data chose to save Akharin, and Rhea's pod was crushed by the black hole.

Finally, Chen realized the Machine Race are using the wormholes to create a work of art that will outlast them. Jean-Luc Picard, Data and Wesley convince the Machine to work with the Travellers and repair the damage to subspace, instead creating a network of travel conduits that will benefit all. Gatt returns peacefully to the main Fellowship, affected by his experience, while Akharin returns to Earth with Data and restores Lal and his own immortality.