If you have multiple copies out(3), are you doing 1 point of damage/sliver to target crea. or player? Or are you doing 3/sliver?
You would be doing 3
Each one will trigger seperatly. In a case where they wouldn't is if they said "Each sliver you control has "{T}: Deal 1 damage to target creature or player"". That would mean only a single could trigger at a time. Since the sliver attacks, all 3 {Thorncaster Sliver}s would trigger seperatly
Resolved!