Irish armies were often supported by non-warriors and youths who, being without normal weaponry, would support their fellow tribe member by pelting the enemy battle line with rocks and whatever else would come to hand. These chaps would be next to useless in a stand up fight but are ideal for causing a steady drip of casualties before your main units charge in.
Irish slingers come in packs of 4 figures chosen from a random pick from 12 different variants.
