Many dwellers here showed mysterious abilities not long after they were born. Some had the power of lightning, some could control plants, some could tunnel into the earth, some could use the chill of frost, and some were capable of communicating with demon beasts...
People with these various abilities would all become warriors, and their abilities were referred to as Martial Spirits.
Martial Spirits were something one was born with, and only very few could acquire a spirit through some stroke of luck. That is why this mainland was named Grace Mainland, as the warriors believed that Martial Spirits were a gift from God.