Energy vortex

Enterprise consumed by vortex.

An energy vortex was a spinning, turbulent local temporal continuum anomaly comprised of pure energy that occurred in space.

In 2365, the USS Enterprise-D encountered an energy vortex near the Endicor system.

According to Data, the encounter with the vortex revealed that was "similar in function to our tractor beam, only more powerful." Deanna Troi was able to sense consciousness, or more accurately "instinct" from the vortex. The vortex probed the Enterprise, with a mass of energy, in effort to determine in the Enterprise and its crew was a life-force. The Enterprise tried to escape the gravitational force of the vortex, only to discover that it was unable to escape the pull while traveling at maximum warp.

Picard attacked by vortex energy.

The Enterprise then attempted to launch a class 1 probe into the vortex, only to have it destroyed. Thereafter, Jean-Luc Picard was struck by an energy beam. After the first attack, Picard noted that "that was personal". Picard then ordered Worf to target the center of the vortex with photon torpedoes, he was again struck by the energy beam. William T. Riker described Picard as being "like a rag in a dog's mouth." It was after this attack, that Troi realized that Picard was the focus of the entity's attention, as it apparently recognized the Enterprise as an entity and Picard as its brain.

In an attempt to save the Enterprise, Picard decides to leave the ship aboard the shuttlepod El-Baz, to distract its attention long enough to allow the Enterprise to escape.

Enterprise destroyed by vortex, in alternate timeline.

In an alternate timeline, Picard left the Enterprise aboard the El-Baz and was thrown back in time six hours, while the Enterprise was destroyed in the vortex.

After the Enterprise encountered the future Picard, it experienced the encounter with the vortex once again, only with a different outcome. Picard stopped his future self from leaving the Enterprise and turned the ship into the vortex, freeing the ship from it, and allowing it to resume course to the Endicore system. (TNG: "Time Squared")

Background

The explanation for the apparently sentience of this vortex, which was described to be associated with Q, was removed after Maurice Hurley's original script for was heavily rewritten.

According to the Star Trek: The Next Generation Companion, ""Time Squared" would segue into "Q Who" (142), in which the mischievous superalien is revealed as the cause of the vortex. The plan was scrapped at Gene Roddenberry's insistence, Hurley had said, and so adds confusion to the ending. Why would going into the vortex's center save you? Hurley asked. It doesn't make sense. But it does if Q is pulling the strings."