The king of the lilu wind demons of Assyro-Babylonian tradition: canine face, bulging eyes, scaled body, four wings, scorpion tail, and the right hand raised in the gesture preserved on a hundred amulets. Pazuzu personified the southwest wind that brought fever, drought, and locusts up from the Persian Gulf.
The tradition's great nuance — flattened by modern film — is that Pazuzu was as much invoked as feared. Mesopotamian households wore and hung his image deliberately, because the one force reliably crueler than Pazuzu was the demoness Lamashtu, who preyed on pregnant women and infants — and Pazuzu was her enemy. Amulets show him driving her back to the underworld. He is the ancient world's clearest case of apotropaic logic: set a demon to catch a demon.
His modern fame arrives through The Exorcist (1973), whose possessing entity is identified by the St. Louis-adjacent case's fictionalization as Pazuzu — an attribution with no basis in the Mesopotamian record, where he possesses no one and guards doorways. The archive keeps the file to correct exactly that kind of drift.