A ring is 1 of 5 named concentric rings on the board (Forest, Archer, Knight, Swordsman, Castle).
The outermost ring is the Forest. This ring has the arc numbers on it. The numbers are where the Monsters will start on the board.
The next ring is the Archer ring. The Knight ring is further inward. And the Swordsman ring is closest to the Castle.
The center of the board is the Castle ring. This is where the Towers of the Castle are placed.