Two things. I'll go in the order of what I like. I heard about Avatars from Harry's friend. She wanted my help with the Cult, but as you can guess, I've kept from digging into them even with what we've been doing. [The fact of the matter is that while Jason has heard rumors, he doesn't want to be on their radar. He knows better than to do that.]

But she said that all gods, even gods like yourself, will require an avatar. Older gods, from the age of Dadga, can take multiple avatars, but anyone after that cannot.

I've got Clarke looking into what that means.

When you kill the Avatar, you can either absorb the power into a god, or grant that power to the Avatar. Given the Cult's rumored ties to raising a god, I think that might give us an idea of what they're doing. Maybe.