10 Creepiest Star Trek Aliens
7. The Beta XII-A Entity
First depicted in the Star Trek: The Original Series episode The Day of the Dove, the Beta XII-A entity was a non-corporeal being that fed off anger, hatred, and predatory instincts. It also went to great trouble fomenting those emotions in others. It would have loved reality television.
The entity could pass through solid objects at a whim, transform everyday objects into weapons, heal wounds, and manipulate memories.
When the Enterprise and a Klingon vessel encountered the creature, it destroyed the Klingon ship and then manipulated both crews into fighting over the control of the Enterprise so that it could feast on tasty negative emotions. Eventually, the Enterprise crew realized the creature could be thwarted by humor, friendship, and good nature. Kirk and his crew then convinced the Klingons to help starve the creature by laying down their weapons and ending hostilities. The two crews then joined together in laughing the creature off the ship.