|“||A mighty general shall battle with unmatched ferocity to unite his people.||„|
Guan Yu is one of the most famous names amongst the Three Kingdoms era in China. He's known for his extremely long and beautiful beard, having red skin, being the one who popularized the weapon 'guandao/yanyuedao' (lit. weir moon blade) via his personal weapon, the Green Dragon Crescent Blade, in addition of being one of the few figures in China that went from a mortal into being deified as a God in the Chinese Mythology.
Guan Yu, style name Yunchang (or Changsheng depending on if records were spotty or if he changed his style name later in life), was one of the main generals of the Shu Kingdom, founded by his sworn brother Liu Bei. He's very loyal to his brother and if able, will always stick with him no matter what, participating in campaigns against the Yellow Turbans, Dong Zhuo's tyranny, and pretty much anything else. When Liu Bei's rival Cao Cao managed to capture him and persuaded him to serve him, Guan Yu agreed only on one condition: One moment Liu Bei's whereabout was revealed, he would ditch Cao Cao and come back to his brother. And he did, even if Cao Cao showered him a lot of prizes (including Red Hare, which once belonged to Lü Bu).
However, like many men, Guan Yu has one glaring flaw even if he upheld his loyalty to Liu Bei: He's rather prideful and arrogant, which eventually came to bite him back in the ass when he incited the wrath of another rival warlord, Sun Quan of Wu, by provoking them to attack him when they already had problems with his position at Jingzhou. A combination of Underestimating Badassery of the Wu commander Lu Meng and some miscommunication within his own men caused Guan Yu's men to desert him in a most crucial time and he was captured and executed by Wu, costing Shu a good portion of Jingzhou, their strategic domain at the center of China, and it was just downhill for Shu afterwards.
As time passed, values started to shift. In the wake of the turbulence in China after the Three Kingdoms era, people started to latch on the people of Shu, and to appease the government, people started writing pro-Shu stories that gave much praise to them, Guan Yu included, for this one value that was highly revered: Loyalty. For all his flaws above, Guan Yu still valued his loyalty to his brother and the Han Dynasty, making those stories easier to digest. In addition, despite his flaws and downfall, Records of the Three Kingdoms/San Guo Zhi has stated that Guan Yu was a man that exudes honor and merit, spoken highly by friends and foes alike, including Cao Cao and even Lu Meng.
Though Guan Yu himself doesn't physically appear in the game, his legendary weapon, Varatha, can be used by Zagreus. Guan Yu is implied to not yet be alive, as the weapon is deemed by the fates to have a future purpose.