When Equestria's prime defenders have to give up their power, who makes sure that ponies stay safe? A nice little group named the Night Watch is the answer to that.
An assortment of otherworldly warriors appear at seemingly random throughout Equestria, or more accurately, Ponyville and Canterlot. As (most) of these aliens wish to leave, they find themselves in rivalry with one another.
As Discord is known for doing, he decides that things are too boring around Equestria, and due to this, he releases a number of strange creatures into the world of ponies, diverse in says, yet similar in one. They all hate Discord. (WoWXMLP)