So aether, how does it work exactly?

[ObsidianFire]

I wouldn't even say aether is finite or non-renewable or in danger of "running out". That's what the entire cycle of aether leaving the Lifestream to be born and then going back to the Lifestream when something dies is all about. I would say that the percentage of where it is and who has it needs to be kept within certain perimeters for the world(s) to function correctly. And the Ascians have been playing around with that for a long, long time.