Intellivore

The intellivore was the designation of a warp-capable planet twice the size of Earth that inhabited the area near the Great Rift.

It survived by absorbing the mental energies and sense of sentience of colonial expeditions to itself and then leaving the area. It was thought to be older than the Milky Way Galaxy itself. It was filled with a tunnel system containing massive warp coils, and contained eighteen hundred pools of antiwater ranging in size from five to ten cubic miles.

It was built by a species that had a partially-joined hive mind. They began to die off and became unable to reproduce. One member of the race discovered that by devouring the energies of other minds, one could trick one's own mind out of the knowledge of its own mortality. At first they preyed on each other and then on other species. These species unleashed devastation on the homeworld in retribution. Thus, they built a mobile planet over a period of a thousand years and stored their minds in matrices. After devouring all life in their home galaxy, it traveled through the void to a primitive star cluster. It waited until this cluster became the Milky Way Galaxy and species populated it, then began to feed once more.

It inhabited the Great Rift for some time until it was destroyed by the U.S.S. Enterprise-D and the U.S.S. Marignano in 2371 with a planet-cracker bomb.

It may have been the Iruhe encountered by the Romulans during their exodus to Romulus. Planets it was mistaken for include 22 Ophiuchi, 334 Scorpii, 1440 Ophiuchi B V, B Hydri, and Iruh.

(novel: Star Trek: The Next Generation: Intellivore)