Shu is a posture. Egyptian art shows him kneeling or standing with both arms raised, palms flat, holding the sky off the earth — and that gesture is not something he does occasionally but the permanent condition of the world. Remove him and the universe closes. He is the first god produced by Atum, and what he embodies is the space between: air, the dry luminous atmosphere, and the interval that allows two things to be two things.
His name is written with a feather, though not the ostrich plume of Ma'at — his is generally shown as a single upright feather in his hair. The Pyramid Texts pun his name against a word for spitting or sneezing, one of the two mechanisms by which Atum produces him and his sister Tefnut from his own body.
Separation as a cosmic act
Egyptian cosmogony does not begin with the making of things; it begins with the making of distinctions. Before creation there is Nun, an undifferentiated wet dark in which nothing is separate. Creation proceeds by division: light from dark, land from water, sky from earth. Shu is the agent of the last and most consequential of those divisions, and it is why the image of him between Geb and Nut is the single most reproduced cosmological picture from Egypt.
He is usually shown assisted, most often by two ram-headed figures, and in the Book of the Heavenly Cow by eight heh gods who steady the legs of the sky cow when she rises too high and becomes unsteady. So the arrangement is not one god's brute strength. It is a supported structure with named components — closer to an engineering diagram than to a feat.
Headrests, the wooden crescent-on-a-stalk that Egyptians slept on and were buried with, sometimes carry Shu's figure carved into the support, arms raised. The object holds up a head the way the god holds up the sky, and the pun is deliberate: several surviving examples show him with a solar disc, making the sleeper's head the sun rising over the horizon of the shoulders. It is one of the more elegant pieces of visual wit in Egyptian design.
The lion, and the pair
He and Tefnut are frequently shown as a pair of lions seated back to back, facing opposite directions, with the sun disc rising between them — the Akeru or the double-lion horizon. Facing east and west, they are the two horizons, yesterday and tomorrow, and the sun passes between them. This is a genuinely old image; a wooden headrest and a pectoral from Tutankhamun's tomb both use the motif.
The lion form makes Shu a solar deity in his own right — the sunlight itself, the dry heat of the air — and in some texts he is called the son of Ra rather than of Atum, which is the same claim once Ra and Atum have been merged at Heliopolis.
The king who ruled after Ra
There is a strand of Egyptian material, developed in the Late Period Book of the Fayum and related texts, in which the gods reigned as kings on earth in sequence, and Shu takes the throne after Ra withdraws to the sky. His reign ends badly: the followers of Apep or a rebellion of foreign enemies attacks, there are storms and darkness for nine days, and Shu eventually ascends to the sky himself, leaving Geb to succeed him. It is one of the few Egyptian narratives that treats the divine dynasty as a political history with reigns, disorders and successions, and it exists precisely because Egyptian kingship needed a continuous line running from the creator down to the current occupant of the throne.
Almost nowhere, and then Amarna
Like several of the structural deities of the Ennead, he has effectively no independent cult. He appears in the temples of others, in headrest amulets, in coffin decoration and in the standard cosmological scenes, and there is no pilgrimage centre, no dedicated priesthood of note and no annual festival. Leontopolis in the Delta, where a lion cult operated, is his and Tefnut's most substantial cult association.
There is one striking exception to his obscurity, and it belongs to the Amarna period. Akhenaten's theology, which reduced the pantheon to the Aten, retained Shu and Tefnut in a modified form — the royal couple were identified with them in Amarna iconography, and Shu's association with light and air made him compatible with a religion of solar radiance in a way that most gods were not. A god of nothing in particular survived a purge that took down Amun.
Questions about the god in the middle
Is he a god of wind?
Not really, and the distinction matters. Egyptian has other terms and figures for wind as a moving force; Shu is air as a medium — the transparent stuff that fills the gap, the breathable substance, the light-carrying atmosphere. In funerary texts the dead ask for the breath of Shu, meaning respiration, and the same word for breath is what the ankh delivers when a god holds it to a king's nose. A god of wind would be a weather deity; Shu is closer to a physical constant.
Why do Egyptian texts pun on his name?
Because Egyptian religious writing treats similarity of sound as evidence of connection rather than as coincidence. If the word for the god resembles the word for spitting, that resemblance is understood to reveal something real about how he came to be. This runs through the whole corpus — the sun god's names, the goddess of the throne whose name is the throne sign, the harvest and destiny sharing a word in Renenutet — and it means that a translation which smooths out the wordplay loses part of the argument the text is making.
What happens if he lets go?
The texts imply, without dwelling on it, that the sky would fall onto the earth and creation would end — which is the same terminal state described in the Coffin Texts passage where Atum finally returns everything to the waters. Egyptian cosmology is permanently contingent: the sun's nightly voyage can fail, the balance can go wrong, and the sky is held up by an act that has to keep being performed. The Duat page follows the same premise into the night journey, where the maintenance of order is explicitly somebody's nightly job.