"Soul is a weapon-based fantasy fighting game series by Namco Bandai Games. The series revolves around a sword that, after years of bloodshed and hatred, gained a soul of its own, the Soul Edge, and the sword forged to counter it, Soul Calibur. The series is special in that each character is created to have his or her own unique weapon and style creating a varied fighting experience. The series links with the Tekken series as one of the characters is a descendant of one in this series."
Source: Wikipedia, "Soul_(series)", available under the CC-BY-SA License.