While barbarians are peaceful at low levels, they become aggressive starting at Level 10. They may launch counter-attacks on your cities as retaliation for your raids. Rebuild Time:
Also, in competitive servers, the player who controls the barbarian rotation controls the resource market. While your enemies are mining slow marble, you are pillaging 50,000 sulfur per hour. ikariam barbarian village attack guide
These levels serve as a tutorial. There is no wall to worry about, and rewards are modest but helpful for early building. Mid Levels (10–29) While barbarians are peaceful at low levels, they