What is Soul Edge?

The Soul Edge is a legendary weapon from a fighting game called Soul Calibur. It is locked in an eternal clash with the Soul Calibur; in this clash, the Soul Calibur represents benevolence, the Soul Edge malevolence. All the characters considered "good" are fighting for the Soul Calibur, while the characters fighting for the Soul Edge are "evil".

Like the Soul Calibur, it has the ability to take the form of whatever weapon its holder uses.