Question: What demon from Assyrian and Babylonian mythology is battled by Father Damien Karras in "The Exorcist" film series? 

Context articles: Babylonian religion
Lankester Merrin
Damien Karras
Nammu
Jason Miller (playwright)
Father Damien Statue
Asakku
Pazuzu (The Exorcist)
Enki
Pazuzu (disambiguation)

Babylonian religion is the religious practice of Babylonia.
 Babylonian mythology was greatly influenced by their Sumerian counterparts, and was written on clay tablets inscribed with the cuneiform script derived from Sumerian cuneiform.
 The myths were usually either written in Sumerian or Akkadian.
 Some Babylonian texts were translations into Akkadian from the Sumerian language of earlier texts, although the names of some deities were changed.
Merrin, an elderly priest and paleontologist on an archeological dig in Iraq, finds images of the demon Pazuzu and subsequently experiences other unusual phenomena.
 He had previously faced the demon many years ago during an exorcism in Africa.
 The find sparks a premonition that he will battle the demon again in a distant land.
 Merrin does not appear again until much later in the novel, when he joins the protagonist, Father Damien Karras, in Washington, D.C. to exorcise the demon from the body of a young girl.
 Merrin, who has a heart condition for which he takes nitroglycerin, dies during the ritual, leaving the inexperienced Karras to complete the exorcism himself.
In William Peter Blatty's "The Exorcist", Father Karras was one of the priests who exorcises the demon from young Regan MacNeil.
 He is a Jesuit psychiatrist suffering a crisis of faith.
 He searches for proof to lead an exorcism, yet during his investigation he comes to realize that there is no better way for God to prove His own existence than to reveal the foul presence of a demon.
 During the exorcism, the demon frequently brings up the subject of Karras's mother's death and how he wasn't there to see her die, which seems to trouble Karras emotionally.
In Sumerian mythology, Nammu (also Namma, spelled ideographically 𒀭𒇉 NAMMA = <a href="engur">ENGUR</a>) was a primeval goddess, corresponding to <a href="Tiamat">Tiamat</a> in <a href="Babylonian%20mythology">Babylonian mythology</a>.
Jason Miller (April 22, 1939May 13, 2001) was an American actor and playwright.
 He received the 1973 Pulitzer Prize for Drama for his play "That Championship Season" and was widely recognized for his role as Father Damien Karras in the 1973 horror film "The Exorcist," a role he reprised briefly in "The Exorcist III."
 He later became artistic director of the Scranton Public Theatre in Scranton, Pennsylvania, where "That Championship Season" was set.
The Father Damien Statue, also called the Saint Damien of Molokaʻ i Statue, is the centerpiece of the entrance to the Hawaiʻ i State Capitol and the Hawaiʻ i State Legislature in Honolulu, Hawaiʻ i.
 A second bronze cast is displayed in the National Statuary Hall Collection in the United States Capitol along with the Kamehameha Statue.
 The landmark memorializes the famous Hawaiʻ i Catholic Church priest from Belgium who sacrificed his life for the lepers of the island of Molokaʻ i.
 Father Damien is considered one of the preeminent heroes of Hawaiʻ i, and was canonized by Pope Benedict XVI on October 11, 2009.
 Cast in bronze, the statue depicts Father Damien in his later years after being diagnosed with the disease of those he attended.
 Much attention was given to the recreation of the disfiguring scars on the priest's face and his arm hanging from a sling.
In Babylonian mythology, the Asakku (Sumerian Asag) were one type of Mesopotamian evil spirits and monsters, classed with good spirits as Utukku.
 Asakku demons attack and kill human beings, especially by means of head fevers.
 They are mentioned in poetical enumerations of diseases and are named for Asag, a monstrous demon whom the god Ninurta/Ningirsu defeated using the mystic mace Sharur.
 Other types of demon include the Edimmu.
Pazuzu is the main antagonist in "The Exorcist" horror novels and film series, created by William Peter Blatty.
 Blatty derived the character from Assyrian and Babylonian mythology, where Pazuzu was considered the king of the demons of the wind, and the son of the god Hanbi.
 In "The Exorcist", Pazuzu appears as a demon who possesses Regan MacNeil.
Enki ( ; Sumerian: EN.KI(G) ) is a god in Sumerian mythology, later known as Ea in Akkadian and Babylonian mythology.
 He was originally patron god of the city of Eridu, but later the influence of his cult spread throughout Mesopotamia and to the Canaanites, Hittites and Hurrians.
 He was the deity of crafts ("gašam"); mischief; water, seawater, lakewater ("a", "aba", "ab"), intelligence ("gestú", literally "ear") and creation ("Nudimmud": "nu", likeness, "dim mud", make beer).
 He was associated with the southern band of constellations called "stars of Ea", but also with the constellation AŠ-IKU, "the Field" (Square of Pegasus).
 Beginning around the second millennium BCE, he was sometimes referred to in writing by the numeric ideogram for "40," occasionally referred to as his "sacred number."
 The planet Mercury, associated with Babylonian "Nabu" (the son of Marduk) was in Sumerian times, identified with Enki.
Pazuzu is king of the demons of the wind, the bearer of storms and drought, in Assyrian and Babylonian mythology.