I am writing a short story on /r/FinishInTheComments with another guy and sent it down an interesting path. This is science fiction so obviously it is, well, fiction, but I,would like,the mythology to be somewhat accurate. I had never heard of this particular deity so any information that does not show up on Wikipedia would be helpful. Thanks in advance, and if you are into that sort of thing here is the ongoing story. Also any story ideas would be welcomed, but given this is AskHistorians, I limit question to to the history of Assyrian mythology.
Namtar is a pretty minor deity in the general scheme of things; I'm not sure he even had any independent cult centers. He shows up in the myth Nergal and Ereškigal as a sort of vizier to the lady of the netherworld Ereškgal, in which capacity he is a sort of messenger or emissary between Ereškigal and the gods in heaven and conveys her requests and messages. His other notable appearance in a narrative literary text is in the "Netherworld Vision of an Assyrian Crown Prince", an extremely bizarre text in which an Assyrian prince is given a tour of the netherworld and its demons. In this text, Namtar is described as Ereškigal's vizier:
I saw Namtar, the vizier of the underworld, who fashions the visceral omens; a man stood before him, while he held the hair of his head in his left hand, and wielded a dagger in his right [...]
The first part of this description refers to Namtar's association with fate as well as the underworld; he lends his name to the Sumerian word for destiny or fate. Both of these texts were circulated in Assyria; the Netherworld Vision of an Assyrian Crown Prince was part of the estoteric and somewhat strange literary production of the late Assyrian court while Nergal and Ereškigal is known both from the Middle Babylonian and Neo-Assyrian periods. He is also given an offering as "decreer of fates" in The Death of Ur-Namma, although I am not sure that text was known in later Assyria. Outside of literature, Namtar appears most prominently in exorcistic literature; hence he is addressed as a powerful demon in the compilation UDUG.HUL(but just that, a demon) and in a ritual against ghosts from Sultantepe a man's Namtar" is addressed (here Namtar in the sense of fate rather than a personified demon). But in general, Namtar is not the post powerful figure associated with death and disaster in Mesopotamia; more prominent are the demons and guardians of the gates of the netherworld Lugalgirra and Mesalamtea, the warrior/pestilence god Nergal with whom Lugalgirra and Mesalamtea were often identified(and whose cult center at Kutha had considerable prominence) and the god of plague and famine Erra.