Energy, elemental and non-physical types

Some catalogued types have little or no body in the ordinary sense. The Arcturian of channelled literature is described as small, blue-skinned and partly non-physical, oriented toward healing. The Celestial is the light-bodied mentor of religious and New Age tradition. The Shadow figure is the dark silhouette reported at the edge of vision, a phenomenon well studied in connection with sleep paralysis. The Crystalline extends astrobiology's silicon-life thought experiment, and the Elemental descends from the fire, earth, air and water spirits codified by Paracelsus in the sixteenth century.

Arcturians are small, luminous and described as healers; Celestials are beings of pure light met in near-death and visionary experience; Shadows are dark, featureless figures glimpsed at the bedside or the edge of vision; Crystalline beings are the silicon life of fiction; Elementals are the nature spirits of Paracelsus reinterpreted as alien. What unites them is that no body is reported, only a presence.

Beings of light and shadow are the oldest experiences in the group: angels, demons, the 'old hag' of sleep paralysis, the fairies of Vallée's Magonia. The New Age rebranded the light beings as Arcturians and ascended masters in the 1980s; the internet gave the shadow figures a name, and a hat, in the 2000s.

This family is where the UFO subject overlaps most with religious experience and with sleep science. Sleep paralysis accounts for the bedside figures; near-death physiology and expectation account for the beings of light; the rest is metaphysics or fiction. The Atlas files the family as folklore and speculation and points readers to the explanations page.