Rule of Burning Iron

Cast on 3+ Burning Iron is a magic missile with a range of up to 24". If successfully cast, the spell hits a single model (chosen by the caster) and causes 1 S3 hit if the target has no armour save or a save of 6, 1 S4 hit if the target has an armour save of 5+, and 1 S5 hit if the target has an armour save of 4+ or better. This is a Fire attack and causes double damage against flammable targets.