Ganging up allows attackers to flank, exploit openings, and generally harass a foe. Each additional adjacent foe (who isn’t Stunned) adds +1 to all the attackers’ Fighting rolls, up to a maximum of +4. If three goblins attack a single hero, for example, each of the three goblins add+2 to their Fighting rolls.

Each ally adjacent to the defender cancels out one point of Gang Up bonus from an attacker adjacent to both. This means troops in opposing lines, such as a medieval formation where each man has three adjacent foes and two adjacent allies, don’t get the bonus unless actually flanked.