A vast crystalline lifeform that drifted between worlds, stripping them of all organic matter and converting it into energy.
The Crystalline Entity was an enormous spaceborne being built from a lattice of crystal, glittering like a giant snowflake. It fed by sweeping over a planet and converting every living thing on its surface into energy, leaving the world barren behind it.
In Datalore, the crew learned that the android Lore had lured the entity to Omicron Theta, where it wiped out the colony that had built him and Data. Lore later tried to deliver the Enterprise to it as well, until Wesley Crusher beamed him into space.
In Silicon Avatar, the entity struck a new colony on Melona IV. Picard hoped to communicate with it, but Dr. Kila Marr, whose son had died on Omicron Theta, used a modified graviton beam to shatter it, destroying the being before contact could be made.