Battle at The Emerald Wall. Kingdom Chronicles, #10

After a failed ritual, The Black Unicorn roams freely, seeking to reclaim the world. The Emerald Wall is the first line of defense for all of the mainland Kingdom. Ancient and strong, it is controlled by the Emerald Watch. For Commander Kurath, it's just another day... until the sun goes down, and a mysterious storm over Culex Island signals that something is wrong. It's the only warning they get.
It doesn't take long before the monster arrives, bringing a horde of hungry unicorns with him. As the night devolves into a fight for survival, Kurath and his troops are locked into battle with a force no one in living history has ever faced.