Fairy Law 

 

Fairy Law

An improved version of Law that when activated, results in the production of a bright light that envelops the area and inflicts massive damage only on whoever the caster perceives as an enemy, leaving friends and bystanders completely unharmed. The judgement of whether someone is friend or foe comes from the user's heart, and they cannot lie to this Magic. It is considered one of the most powerful Magics and is one of the rare legendary spells.

The Magic's strength was so great that it defeated Jose Porla, a Wizard Saint, in a single blow, during the final battle in the Phantom Lord vs Fairy Tail guild war. According to the second master of Fairy Tail, Precht, Fairy Law is a deterrent Magic, meant to discourage further action from enemies, and is not something that should be used lightly.

Setting Law as its basis, Mavis modified and improved it so that users wouldn't suffer from its side effect,but she has noted that this Magic is meant to only be used against a singular target, the more targets the caster uses it on, the more likely it would be lethal to their lifespan, and in the worst cases can cause the death of the caster.