This hero built has only two binding spirits so that with soul twisting you can basically count on always having shelter and union up. With three binding rituals the soul twisting would be quickly used up and the hero would then use the binding rituals again if the spirits went down in battle, leaving you with a wait to have them recharged again. With only two binding rituals you will virtually always have at least one of the two up, and most often both. Hence the limitation of only two binding rituals in this hero built.