Yu Shin

Past Timeline
He is a former leader of the Hwarang army who later lost a battle and thus his title of “leader”. He goes to the mountains after being shunned by others but returns after he heard his town was in danger. He eventually transcends into a sage. Bi Dam becomes the leader of the Hwarang army later on.

He knew Karma from a long time ago as they were sages. Yu Shin was the one to help Karma learned how to write which is how he sends a letter to the Seven Knights in season 1.

Season 1
He's a close friend of Karma and he was the one who defeated him which made him move to the mountains. However, Karma and Yu Shin still hold a lot of respect for each other.

Season 2
Lee Jung sends a letter to Bi Dam asking him to look for Nezha and Yu Shin who seem to have been kidnapped. It is revealed that the Dark Magic Research Tower were the ones to kidnap him along with Nezha. Yu Shin is experimented on and completely changes from his old self. He was brainwashed by the Dark Magic Research Tower and becomes a fallen sage.



His strength increases incredibly and becomes the strongest normal hero of all.

Season 3
Awakened Karma's power is said to rival that of Yu Shin's awakening. Yu Shin appears in Karma's awakening scenario and attacks him as he's been changed mentally. However Karma is able to heal him and cure him from the awakening power which makes Yu Shin reverse into an unawakened form. However, Karma has to merge with Shadow Karma in order to save Yu Shin.

Trivia

 * Only character in the story which awakens and unawakens again.
 * As of January 2019, Awaken Yu Shin is called the strongest normal hero in the storyline.

Season 1

 * Bai Jiao: "Treacherous subject."
 * Lee Jung: Wise leader
 * Kang Jae: Pitiful soul

Season 2

 * Velika: Obeys