If there are three duplicates: A roll of 1-5 will hit the caster, a roll of 6 or higher will hit a duplicate
If there are two duplicates: A roll of 1-7 will hit the caster, a roll of 8 or higher will hit a duplicate
If there is one duplicate: A roll of 1-10 will hit the caster, a roll of 11 or higher will hit a duplicate
The threshold for targeting a duplicate decreases as the number of duplicates remaining decreases. If an attack hits a duplicate, it is destroyed. If all duplicates are destroyed or the attack roll is too low to target a duplicate, the attack targets the caster as normal.