My Contract Turned Out to Be a Zombie

200 Years ago, tens of thousands of meteorites fell to the earth, and many terrifying monsters popped out of them. They wreaked havoc on cities and massacred civilians. For the survival of mankind, the five United Nations built underground cities while resisting monsters. Finally, all mankind entered the underground city life. One day, those tens of thousands of meteorites turned into a cloud of green smoke and floated into the atmosphere. In another large-scale beast tide, mankind was defeated and was about to be swallowed up. When it was about to be engulfed, a man riding a dragon came out, becoming the first person in human history. Tamer