Eridios was a planet.

In 2257, Christopher Pike, in command of the USS Enterprise, had the planet's surface destroyed in an effort to prevent space-time from disintegrating. The incident led to the creation of General Order 24. (Last Unicorn RPG module: All Our Yesterdays: The Time Travel Sourcebook)

planets visited by the USS Enterprise (NCC-1701) (2243-2264)
Robert April's command (2243-2251)	Earth • Romulan planetoid • Tarsus IV • Faramond
Christopher Pike's command (2251-2264)	Earth • GS391 • Areta • Magefferus III • Pharos siteworld • Rigel VII • Talos IV • Darien 224 • Prairie • Neyda Prime • Liria • Jubal • Theta Kalyb • Algol II • Temazi • Corinthia VII • Eridios