Planet X

Planet X is a hidden planet, in the far reaches of the Terran Solar System in Ultima II. Castle Barataria (where Father Antos can be found) and Towne Basko are both located here as well.

In New San Antonio the Stranger learned that, in order to get the Force Field Ring, the blessing of Father Antos was needed before the old man who owned the ring would sell it. Using a rocket in the time of the Aftermath, the Stranger warped to Planet X and found Castle Barataria, getting Father Antos' blessing to receive the ring.

Planet X is not on the space chart found in the documentation. Its coordinates are 9,9,9.

Trivia

 * In reality, Percival Lowell, the astronomer seen in Martian Dreams, was the originator of the Planet X theory.