Angel, those who blossomed their spiritual power into "transcendental power". Guardian, those who blossomed their spiritual power into "absolute power".
People that possessed both characteristics started to appear in White World after the "Gambiel War" that thrown the White World into unprecedented crisis. They are called "Radiant Saint" after the "Ten Radiant Saints"—a group of promising people with both outstanding talents and distinguished war service in the previous war.
They are characterized by weapons and armors made of spiritual power (spiritual arms) similar to the Guardian, and wings composed of light particles. Since they are different from the Angel, they didn't manifest halo above their heads, and the size of their spiritual arms isn't gigantic like the Guardian. Whether they are a subspecies of the Angel or the Guardian, or should be categorized as a new Tribe, has caused debates among the experts.
While the "Ten Radiant Saints" are technically part of this group (and also being the original namesake), they only possessed a single Tribe instead of dual Tribe and treated as separate group in the story.