Throughout its history the planet Eamon has been magically connected to numerous other planets and planes, so the presence of beings from other worlds is a common and unsurprising fact of life for many Eamonites. However, some beings occasionally reach the world not through magical rifts or portals but by traveling across the vast interstellar void in spacecraft, and these are the visitors that the Guide (and most Eamonites) refer to as "aliens".
Scholars know of a handful of such visitations, including the Yag in deep pre-history, the Gems in the sixth millennium BA, and the Celtharians during the Grey Year; various others are attested in legends and anecdotes. So far as is known, none of the visitations have led to permanent colonization or the presence of any significant alien population on Eamon.
