An uninhabited Class M planet whose caverns concealed the hiding place of the alien boy Barash.
Alpha Onias III is an uninhabited Class M world near the Romulan Neutral Zone. Unusual readings from a large cavern on its surface draw an away team of Riker, La Forge and Worf to investigate, and the cave fills with gas that renders them unconscious.
In Future Imperfect, the planet turns out to be the refuge of Barash, an alien child left there by his mother. Machinery hidden beneath the surface allowed him to create elaborate illusions, which he used to trap Riker in a false future aboard the Enterprise and later in a fake Romulan prison.