This makes me wonder if we could find some way of diverting a reflections aether sea to feed back into the source could that cause a non cataclysmic rejoining. Beings would die off, but then flow back to the Source preventing new life from occurring on the reflection.

But to go with original question I think voidsent are so far gone that when killed they fully die meaning soul and aether too. Would also explain why the Ascians considered the world a lost cause. No hope of anything there ever being rejoined no matter what method used.