When the Third Doctor and Jo Grant visited Verd, it had several gravitic anomalies, manifested most strongly in several numbered "gravity wells". During their brief visit, the gravity problems became much more severe, and the satellite's orbit decayed sharply. It appeared as though the moon was on a collision course with Galaxis Bright's atmosphere.
Simultaneously, the moon's other inhabitant, a Norebo Worm the locals called the "Nightdreamer King", was beginning to use its natural telepathic abilities on whatever minds it could find around it. Finally, it locked onto the mind of the Doctor, who then confirmed his suspicions as to the true nature of the moon. It was, in reality, a cocoon. From a safe distance, the Doctor and Jo witnessed the moon explode after the Norebo Worm transformed into a massive, butterfly-like creature of extreme beauty. After using its psychic abilities to bestow good will onto the recently-displaced humanoid population that had been forced to evacuate their homes on Verd, it disappeared. (PROSE: Nightdreamers)