Isku was a storm god, Mesopotamian (Sumerian) [Iraq); worshipped from about 3500 BC, probably earlier, to 1750 BC and his cult center was Karkara. This deity was the major thunder and rain god of the herdsmen, and is described as the brother of sun god Utu. In creation mythology Iskur was given charge over the winds, the so-called "silver lock of the heart of heaven," by the god Enki. Other authors state that in prehistoric times he was perceived as a bull or as a lion whose roar is the thunder. He may be depicted as a warrior riding across the skies in a chariot, dispending raindrops and hailstones. In one text he is identified as the son of An and twin brother of Enki. He has been compared to Nimurta, the primary god of the farmers. He was also adopted by the Hittites as a storm god. A.G.H.
Jordan, Michael, Encyclopedia of Gods, New York, Facts On File, Inc. 1993, pp. 118-119