The Crystalline Entity is a recurring antagonist in Star Trek: The Next Generation. It is the secondary antagonist of the episode "Datalore" and one of the two main antagonists (with Kila Marr) of the episode "Silicon Avatar".
The Crystalline Entity was a giant space-going entity which possessed a voracious appetite. Needing large quantities of minerals to survive, it would attack planets and strip them of all life, leaving just barren rocks. Lore summoned it to the Federation colony Omicron Theta, where it wiped out nearly the entirely population, something for which Lore claimed he was rewarded. When Lore was later retrieved and reactivated by the Enterprise, he summoned the Crystalline Entity to attack the ship. He nearly succeeded in tricking the crew into lowering shields but was defeated by Data and Wesley Crusher. Deprived of a chance to feed, the Crystalline Entity departed.
Despite this, the entity continued to attack Federation planets: By four years later, there had been eleven reported attacks. It assaulted a colony the Enterprise had been helping set up, killing two colonists and stripping the planet of all vegetation.
Doctor Kila Marr, the Federation's expert on the Entity, joined the Enterprise. She considered it to be evil and wanted it destroyed but Picard felt it was merely doing what it needed to survive and possibly didn't understand the impact of its actions. He favoured attempting to communicate. Data and Marr worked out a way to possibly communicate using resonance pulses.
After failing to save a freighter from attack, the Enterprise managed to lure the Entity to it and attempted to communicate by sending out the pulses. The Entity appeared to respond, but before understanding could be achieved, Marr altered the pulses to a frequency and deliberately destroyed the creature.
Throughout its first episode, "Datalore", the creature was referred to as the Crystal Entity. It changed to Crystalline Entity when Lore reappeared in "Brothers" and that name was retained when the creature reappeared in "Silicon Avatar".