A free app for Android, by Indrasoft HK.

Annulus is a dark wind chess strategy mobile game that allows players to play for a long time with a high degree of freedom and enjoyment. It is also a strategy game, but its gameplay is based on the rules of chess. In this game, players will play the role of the head of a mercenary regiment. They will collect and cultivate resources such as mercenaries and weapons with unique attributes, and create their own mercenary regiment.

The battle is not limited by time or space. It is an open world, and players can travel freely from one location to another.