The Enemy Is at the Gates, and I Have Xingtian Armor

Zhou Ping'an is a dashing young man fresh out of school when he unexpectedly transmigrates to a small kingdom in another world and ascends the throne. With the kingdoms locked in conflict and flames of war raging everywhere, he feels humiliated as the ruler of a weak little nation. Just as the enemy army closes in on the city, a chat group miraculously appears. With the generous help of its members, he obtains the Xingtian Armor, turns the tide, and saves his kingdom from crisis.

The worlds that will appear later include Xingtian, Super God, The Smiling, Proud Wanderer, and more.