For generations the second born child of the Lion King has always been the leader of the Lion Guard; a team of animals who's duty is to protect the Pride Lands and the Circle of Life, another reason why the second born child of the Lion King is the leader of the Lion Guard, is because they possess the Roar of the Elders; an intensely powerful roar that is bestowed on them by the Great Kings of the Past.
During the reign of Ahadi, his youngest son Scar was leader of the Lion Guard and was blessed with the power of the Roar. However, Scar let the power get to his head to the point where he believed he was worthier of being king than his older brother Mufasa. He tried to get his team to help him become heir to the throne. When the rest of the Lion Guard refused, Scar destroyed them using the Roar. However, because he used the Roar for evil, Scar lost it and the abilites it gave him forever, resulting in him becoming shrivelled and horrible.
When Mufasa became king, he only had one child named Simba. Because of this, many Pridelanders believed that the Roar and the Lion Guard were gone forever. However, after becoming king, Simba had two children Kiara and Kion. Being the second-born, Kion inherited the Roar and afterwards assembled the new Lion Guard.
List of Known Powers and Abilities
Sonic Roar: When the leader of the Lion Guard uses the Roar of the Elders, all the ancient lion kings roar along with him/her, instilling real power in the roar. With this roar he/she has flattened plains, held floods back and torn down rock-slides. In "The Lion Guard: Return of the Roar", it is revealed that the roar is so powerful it can kill the user's opponent(s); as Scar destroyed the previous Lion Guard when he used the power of the roar.
Lion Head Mark: Who ever the leader of the Lion Guard chooses to become his/her team, he/she marks them with a lion head, symbolizing their positions as members of the Lion Guard, when the leader of the Lion Guard inherits Roar of the Elders; a lion head automatically appears on his/her left shoulder.
Precision: In "Never Roar Again", it is revealed that the roar can be used to hit precised targets. For example, when Makuu and his fleet took Nala hostage she encouraged Kion to use the roar and when he did instead of using it on everything, he controlled it to only take out Makuu's fleet.
Evil Deeds: If the leader of the Lion Guard ever uses the Roar of the Elders for evil, he/she will lose this power permanently.
The first mention of this ability was in the book Hear Me Roar!.
When Kion uses the Roar, he always tells everyone to get behind him. But in the title sequence, Bunga is clearly in front of him, and therefore should be blasted forward. This happens again in Janja's New Crew, though Kion is behind the Guard, none are affected when he uses the Roar.