Yun Canghail (云沧海) is the former patriarch of the Yun Family. He is the father of Yun Qinghong and Yun Che's grandfather. He was imprisoned under a seal formation at the Heavenly Sword Villa and after Yun Che became trapped in the same formation, he killed himself release the formation and save his grandson.
He is Yun Che's grandfather and formerly the Patriarch of the Yun Family. He was the 2nd most powerful in terms of profound strength in the entire Illusory Demon Realm. He led the Yun Family and also led the Twelve Guardian Families that protect the ruler of the Illusory Demon Realm, the Demon Emperor. He was close friends with the emperor and was given the title of "Demon King" as a reward for his loyalty and service.
A hundred years ago, the Demon Emperor went missing and was supposedly captured in the Profound Sky Continent. He and 10 of the strongest Yun Family Grand Elders traveled to the Profound Sky Continent to look for the Demon Emperor but they were ambushed by the Mighty Heavenly Sword Region. Yun Cangahi was the only one left alive and eventually imprisoned within the formation beneath the Heavenly Sword Villa’s Sword Management Terrace.
He was the "demon" that has been sealed within the Heavenly Sword Villa’s Sword Management Terrace, by a profound formation called the Heaven’s Might Soul Suppressing Formation. When Ling Kun led the Blue Wind Empire delegation to witness the re-strengthening of the seal formation, he was enraged by Ling Kun's goading and lashed out with his limited profound strength. He saw Xia Yuanba was the weakest in attendance and chose to vent his rage on what he saw was the enemy. He was able to pull Xia Yuanba in with his profound energy. Yun Che rushed into save Xia Yuanba and ended up being sucked into the seal formation himself. Yun Canghai landed a killing blow on Yun Che as the seal formation was completed.
He was surprised that Yun Che was not actually dead and had recovered enough in 8 days to escape from his clutches. He resolved not to kill Yun Che even though Yun Che was trying his best to kill him because he did not view Yun Che as his enemy. He became very intrigued by Yun Che's mysterious recovery power and profound arts that allow him to exert strength many times higher than his profound strength level. He was amazed that Yun Che was able to withstand the pain of his body being burned to refine the blood and flesh of an Emperor Profound flame dragon.
He spends 16 months together with Yun Che and he eventually developed a close relationship with Yun Che. He admired Yun Che's talent and determination in training and cultivation. He found that they shared the same surname. He helped train Yun Che and showed him his Profound Handle. Yun Che also shared the dragon meant with him. By the end, he even was willing to entrust Yun Che with his secrets.
He eventually discovered that Yun Che was his grandson. He happend to see the Mirror of Samsara in Yun Che's possession and he recognized it as being a treasure of the Illusory Demon Royal Family that was entrusted to the Yun Family Patriarch to protect. Yun Che saying it was left by his birth parents aroused his suspicions and he checked by detecting the unawakened Profound Handle on Yun Che. He was convinced that Yun Che was his grandson and a blood paternity test confirmed it.
— Yun Canghai finding out Yun Che is his grandson
He told Yun Che about the background of his parents, the rise of the Yun Family, the history of the Illusory Demon Realm, and the origin of the Demon Emperor's family. He also told Yun Che about the enemies in the Four Great Sacred Grounds and especially the Mighty Heavenly Sword Region. He helped awaken Yun Che's profound handle prematurely. Most importantly, he entrusted his greatest held secrets to Yun Che. These included the Yun Family Patriarch's Crest, the Demon Emperor’s Seal, and secrets of the royal family.
He felt a sense of happiness and fulfillment for meeting his grandson who was amazingly talented and also brave, dignified, and honorable. He also felt content and at ease after entrusting Yun Che with his secrets. In order to allow his grandson to live and carry out his last wishes, he committed suicide by severing his heart veins. This dissolve the seal formation which was tied to his soul.