Last zone is what Meteion would've seen on her journey through the cosmos, eventually struck with grief and despair and allowed her song to kill whatever's alive and remaining somewhere. Sphene's obsession to keep her people alive in one way or another is no different from Meteion. There's a reason the last zone is called "living memory" because it's just that, a memory, people living as their best memories in their lifetime. Sphene couldn't let it go, and we went there to turn off the lights out to allow these people to rest in aetherial sea.