Ferrum Eques

Ferrum Eques (ぺいらむ えくえす Pe-ramu Ekuesu) is a Caster-type magic that allows the user to morph their skin to be more durable then steel. With said magic, the threat of sword mages is negated save for the elite level ones. Though there is one major requirement to use this magic; one must have at least intermediate mastery over Earth Magic.

Trivia

 * Ferrum Eques is Latin; literally translates to "Iron Knight" in English.
 * For those who have noticed and those who have not. Yes. this magic is inspired by abilties like Earth Release: Earth Spear used by Kakuzu in Naruto and Greed's Ultimate Shield form in Fullmetal Alchemist.