At Nineveh, the god which seems to have been the highest in the celestial hierarchy, is Ilu; his character is no further defined and his symbol is often only the abstract representation of the divinity.
Winged Bull discovered at Arban
(Layard)
In the historical texts of the Assyrian kings we find an enumeration of the great gods who were invoked by the sovereigns of the earth; their number and order is not always constant, but such as they are we can mention: Ilu (Ana), who is often confounded at Nineveh with Asshur; then Bel (Baal); and lastly Anu. These three divinities appear as the reflection of the gods of the superior world, which we have already mentioned, but to which we have been unable to ascribe names. Then follow the gods more particularly associated with the visible world: Sin, the god of the moon; Shamash, god of the sun; Bin (Ramman or Adad), god of the higher regions of the atmosphere, arbitrator of the heavens and earth, the god who presides over tempests.
A series of divinities seems especially given over to the superintendence of the planets: Adar over Saturn, Marduk over Jupiter, Nergal over Mars, Ishtar over Venus, Nabu over Mercury.
Ishtar seems always to have a peculiar and special individuality, notwithstanding that each of the great gods has a spouse who is often invoked with him, and who seems to complete him. The rôle of the great spouses of the great gods is not well understood; with Ishtar we can see Beltis figure, whose name is transformed and often becomes like that of Ishtar, a collective appellation of all female divinities; those whose names seem to have a more permanent character are Zarpanit, the goddess who particularly represents the fertile principle of the universe, and Tasmit, the goddess of wisdom. All female divinities seem to have direct relations with humanity, but they often disappear in the higher and inaccessible world, and then only reveal themselves through secondary influences. Secondary gods, whose number is infinite, are born of these divine couples; a tablet from the Nineveh library gives us the list of twelve sons of Anu with their attributes; of these sons other divinities are born, but their descent we cannot follow. It is so with other great gods.
At Babylon the divinities are the same, but the hierarchy is different; Bel seems to have replaced Ilu (Ana), and Marduk takes the place of Asshur. It is easy to be seen that these theogonies come from a common source, which is every day becoming more accessible to us, but which we have not yet sufficiently explored to know its exact nature.
The artistic development at which the Chaldeans had arrived from the remotest antiquity, allows us easily to suppose that we ought to discover in the pictured monuments that which the texts have not yet revealed to us. Unfortunately we cannot fix upon the meaning of the figures on the engraved stones until we shall have complete enlightenment from the texts. The significance of a symbol cannot be guessed at; also it is the most we can do if from all these representations we are able to recognise the figures of four or five divinities—Ilu, Nabu, Marduk, Ishtar, and Zarpanit. There is, moreover, a special reason why we should be most cautious in our comparisons; we know that when the Assyrians took possession of a hostile town, they carried away the images of strange divinities, and restored them to their possessors, after inscribing on these images the names of Assyrian gods. Therefore we should not trust too much to an Assyrian inscription to fix on the identification of the image of a divinity, as deeds of this nature might have been repeated in every campaign. It is thus, doubtless, that we may explain the fact that, while in the whole of Mesopotamia the abstract idea of the divinity was mentioned by the name Ilu, it appears on the monuments of the Achæmenidæ as Ormuzd.