[I've searched a few times, but I can't find a thread for just discussion of the No-God, but if I'm wrong, someone correct me.]
The No-God has always been my second favorite character in the series, so I do have some off-the-wall theories about it's nature.
Mog-Pharau—"No-God"
Mursiris—“Wicked North”
Tsuramah—“Hated One”
Lokung—The “Dead-God” of the Scylvendi.
Cara-Sincurimoi—"The Angel of Endless Hunger"
These are the names of the No-God that we know of. I think the most interesting of them all is the Ihrimsû name of, Cara-Sincurimoi, "The Angel of Endless Hunger." The name seems to imply two things, first, that the No-God hungers, but also that it is an Angel that hungers. What might such a thing hunger for. Surely, considering the nature of what we know of the Carapace, the No-God eats no corporeal food. What I would hypothesize is that the No-God hungers for is souls.
It has been my personal crack-pot that the No-God is not evil, because the No-God has no agency. It doesn't know what it is doing. To square these two points though, my summation would be that it is no more an animal (in fact, maybe less), fueled by a hunger, blind to the implications of it's action, it kills to eat, but it is simply a device, nefarious only because it's creators made it so.
Also, I would like to lob out the following Nerdanel, that perhaps the No-God was born of collective renunciation. In other words, if we suppose that Fane could 'birth' the Solitary God out of faith, perhaps the No-God is 'born' of apostasy?
Sound off on how bad my ideas are.