An Attacker horn is used in Barbarian Assault to tell the collector what to do. The choices to tell the collector are red, blue, and green eggs. It is received when starting Barbarian Assault and becoming an attacker.
The attacker horn determines the player's attack bonus. Depending on the player's Attacker level, each hit using the correct attack style will deal an additional 1-5 damage, with the exclusion of splashed Magic spells. Without the attacker horn, using the correct attack style will deal no additional damage.