As all had known, the Eagle Wing Sword was the emperor's sword passed on from generation to generation within the Eagle Kingdom. It was also the key to activate the Three Eagle Artifacts. Any human who mastered the power of god could be regarded as the true "Eagle Descendant" and believed to take on the whole state.
In other words, the Eagle Wing Sword symbolized the king of Eagle Kingdom. The one who used the sword was not necessarily the king, but a qualified king must know how to use the sword.
Leon Igor was the only living descendant of the former king; thus he had the legal and constitutional, undoubted right of inheritance. Moreover, he was capable and had a good command of the Eagle Wing Sword. This made him well-equipped to succeed as the king and nothing would step in his way of doing so.