M3X-387 is a planet in the Pegasus galaxy, home to a race of intelligent crystals. It is a rainforested planet and seems to have long nights.


The planet was visited by Lt. Colonel John Sheppard's team in 2007 on a standard exploration mission, during which Sheppard came into contact with one of the crystals, prompting the being inside it to enter his body. After going back to Atlantis, the crystal being moved from body to body, manifesting in the form of Sheppard albeit but with traits of a sociopath which caused each of its hosts nightmares, which eventually resulted in the death of Dr. Kate Heightmeyer. The expedition later took one of the crystals to Atlantis to study it and, after defeating the crystal being, brought the crystal back to M3X-387, where they found out, that many more of this crystals existed. Following this, the planet was very likely closed off for good to avoid a repeat incident. (SGA: "Doppelganger")

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