It served as a cult center of the weather god Ishkur, later known under the Akkadian name Adad, and a temple dedicated to him located there is well attested.
[13] "After he (Utu-hegal) departed (from) the temple of the god Iskur, on the fourth day he set up ... in the city of Nagsu on the Iturungal canal.
He proceeded to the god Iskur (and) prayed to him"[14]While originally referred to with the Sumerian name Ishkur,[15] by the Ur III period he came to be fully fused with Adad, who was already associated with him at least by scribes in pre-Sargonic Mari.
[20] It is also possible that Edurku, “House, Pure Abode”, a sanctuary of Shala attested in a lipšur litany, was similarly located in Karkar and formed a part of the Eugalgal.
[21] The oldest reference to the cult of the weather god in Karkar occurs in a text known from three copies from the Old Babylonian period, but presumably originally composed in the late third millennium BCE, according to which king Utu-hegal of Uruk prayed to him in this city to gain his support in an upcoming battle[22] during his campaign against the Gutians.
[12] He highlights the existence Sargonic administrative texts dealing with rations meant for the ereš-dingir (entum) priestess and sanga (šangûm) priest of Ishkur as possible examples.
[25] The city was considered a major religious site, and offerings to the temple of Ishkur were provided not only from a center of royal administration, Puzrish-Dagan, but also from Girsu and Umma, as documented in texts from the reign of Shu-Sin.
[26] Additionally, a year name of an unspecified king from the Third Dynasty of Ur, according to Douglas Frayne Ur-Nammu, though Shulgi has also been suggested, which mentions the appointment of a priestess of Ishkur who was “chosen by omens” might also be related to the traditions of Karkar.
[8] Additional attestations from the period of the latter ruler's reign include a reference to a daughter of this king being the current high priestess of Adad in Karkar, an administrative text from Larsa mentioning a herd of sheep owned by said god, and two passages in texts from Nippur which reference allotments to a certain Adad-ešar, who acted on behalf of said priestess from Karkar.
[34] Another text, a list of temples, also mentions a ziggurat in IMki, presumably also to be understood as Karkar in this context, but states it was known as Eudegalanna (“House, Great Wonder of Heaven”).
[20] In a fragmentary literary text of the Old Babylonian (or possibly following Kassite) era there is a reference to an uprising by troops that "deposed four kings" at Karkar.