Celestial Britannia is a treatise in astronomy written by Sir John, astronomer and scribe at the Lycaeum. It contains scientific discoveries and astral theories, and is referenced in The Book of Lore and Paths of Destiny. The following passages are from this noted tome.
In the heaven beyond our skies, dwell stars whose numbers are beyond our reckoning. Within our heaven, circling our world, sweeps our bright sun. Ten other orbs trace tight paths around our world. The twin moons Trammel and Felucca are desolate, their light only a reflection of the sun's brilliance.
The other eight orbs are thought by some to be planets like our own. According to the roles they play in our many legends, they have been named for the virtues of the Avatar. The closest is Honesty, followed further out by Compassion, Valor, Justice, Sacrifice, Honour, Spirituality, and Humility.
Many tales are told of knights traveling from towne to towne, even across water, merely by stepping into a wall of light. There are few verifiable reports of moongate travel. However, sifting through those reports that are verifiable, it has become clear they operate as follows.
Each night at the apex of the first moon, Trammel, the eight moongates appear, rectangles of shimmering blue light rising from the ground. They remain until Felucca reaches her apex. While the moongates are open, a traveler entering one will instantly be transported to another moongate in a different locale.
The traveler's destination is determined by the phase of the moon closest to midheaven. Moongate travel is said to be fast and safe; however, there have been confusing and conflicting reports of what transpires when the moons are equidistant in the midheaven. Moongate travelers should exercise caution.
Over the ages, comets, fiery nebulae, have torn through our skies as harbingers of impending doom. They appeared just before the emergence of the Dark Lord Mondain. They heralded the reign of the Enchantress Minax, and they foretold the impending danger of the hellborn Exodus. Now, while we live in the midst of peace and enlightenment, the comets have begun again.
- Despite being written just prior to Ultima V, Sir John is no longer to be found in the Lycaeum (or anywhere else).
- The player is not made privy to the "many legends" in which the other planets play a role.