In ages past, the black obelisks of the Old Gods would herald the coming of their forces. The dark conjurers among the k'thir and n'raqi would utilize these monuments to establish footholds in our world and usher in more of the Old Gods' minions.
Today, we see these very same obelisks littering the battlefields. So long as they stand, N'Zoth's forces will be without end.
Make sure they do not.