Anshar’s role in the conventional genealogy of Anu resulted in his incorporation into the Enūma Eliš.^[9] The text does not explicitly state whether he and Kishar are the children of Lahmu and Lahamu, or instead a second pair of Apsu‘s and Tiamat‘s children.^[10] However, the former option is considered the correct interpretation.^[23] Anshar serves for a time as the king of the gods.^[1] His grandson Ea informs him about Tiamat plotting against the younger deities, which prompts Anshar to blame him and task him with finding a solution.^[24] After he fails, Anshar sends Anu to attempt to solve the issue, but he is similarly unsuccessful.^[25] Ea eventually convinces him that the only god who can defeat Tiamat is his own son, Marduk.^[26] Anshar then summons his attendant Kakka to inform Lahmu and Lahamu about his decision to rely on Marduk.^[27] After emerging victorious, Marduk replaces Anshar as the new king of the gods.^[28] The latter is the first deity to provide him with new names.^[29] He states that Marduk will be known as Asalluhi^[30] and subsequently partakes in further name-giving alongside Lahmu and Lahamu.^[31]

In an Assyrian recension of the Enūma Eliš, known only from a number of incomplete late copies from Assur and Nineveh tentatively dated to the reign from Sennacherib, the logogram AN.ŠÁR is used to refer to both Anshar himself and to Ashur, who replaces Marduk as the protagonist, but is also identified with the aforementioned primordial deity.^[32] As noted by Wilfred G. Lambert, the change is “superficial” and “leaves the plot in chaos by attributing Marduk’s part to his great-grandfather, without making any attempt to iron out the resulting confusion”.^[33] This rewrite might be referenced in a late Assyrian commentary on the Enūma Eliš, which states that Anshar came into being “when heaven and underworld had not been created” but “city and house were in existence”, which reflects the role of Marduk (and thus Ashur) more accurately than that of Anshar himself.^[34]

An esoteric commentary linking passages from the Enūma Eliš with various ritual observances from Babylon states that Anshar sending Anu to confront Tiamat corresponds to the celebrations during which Mandanu headed to Ḫursagkalamma (Kish).^[35]