Instead of attacking normally, the whole unit of Trolls can choose to vomit on the enemy. Each Troll model in base contact with an enemy model inflicts one automatic Strength 5 hit with no armour saves allowed. These attacks are treated as magical.
Source: Warhammer Fantasy: 7th Edition
Instead of attacking normally, the whole unit of Trolls can choose to vomit on the enemy. Each Troll model in base contact with an enemy model inflicts one automatic Strength 5 hit with no armour saves allowed. These attacks are treated as magical.