This story is a sequel to Left Behind
After defeating the Broken Pony, Nightmare Moon is finally free to begin her plans to retake Equestria and restore it to its former glory. However, she is haunted by the ill portents she had been given and searches for signs of her sisters' fragments or the coming of any new alicorns.
On top of this, the king impedes the alicorn's work at every turn and tries to be rid of her just as frequently. So many things happening all at once and spiraling towards the doom the 'leftover tool' warned her about, but Nightmare Moon is determined. No creature will stop her goal, not even the dregs of Equestria's destroyers from so long ago.