How Well Do These Mythical Beings Nagakaboros?

Since Aspects and Ascendants draw their powers from the same source, I've become interested in the magical forces of Runeterra.

Using Nagakaborous for example, we learn that whatever revived Pyke have a connection with the god. We also know that Aurelion Sol is aware of the deity. But what about Targon? Assuming they know what NGK is, why haven't they used its power?

Following on NGK, we know that the Kindred act as Grim Reapers. Do they know of NGK? What about Tahm Kench? He's a demon with knowledge on the world. Do Ionians have their own interpretations of the god, given their connections with the spirit realm?

Finally, what about the demigods? I'm sure they have to have some connection. Why else would they be called demigods?