Astronomical Alignment

The Astronomical Alignment is a very rare event in which all of the planets of the Britannian Solar System, including Britannia and its two moons Trammel and Felucca, are all aligned in one straight line to the sun. One occured during the course of Ultima VII.

Description
The astrological alignment happens only once every eight-hundred years, and it is said to be an event of great mystical significance, weakening the borders between the planes and allowing for great acts of magic to transpire. At the time of the Avatar's first quest against the Guardian, an impending alignment was to activate the functionality of the red titans intended gateway to Britannia - the Black Gate - which was to become operable at the exact moment the planet's aligned.

Fortunately, the hero thwarted the Guardian's plans by using a magical transmuter to destroy the blackrock used in the gate's construction, rendering the portal useless and halting the evil entity's effort to invade Britannia at that point in time.

Trivia

 * Taking the Britannian Calendar into account, the Alignment can only happen during a double new moon, which only happens at the first of a month.