Courtesy name Zhongda. As the acting head of the prestigious merchant clan, the Sima family, even in his teens Sima Yi was acknowledged by many prominent clan figures as a genius strategist, whose foresights and darings top almost all others of his time, and can be said to rival those of the most brilliant military tacticians, the Eight Enigmas. He is also the advisor-commander of the infamous assassin squad, the Crippled Legion, and is friend to its current leader, Liaoyuan Huo. Despite this, he stays concealed most of the time, often under the disguise of a manservant, and only opts to reveal himself when the situation necessitates it.

Spoiler

At a young age, Sima Yi was philosophical - he sees the chaotic era as a time countless fiends roam, and rather than striving to bring peace (true to the ideals of most men), he stays overall unconcerned towards anything other than developing his family business. This attitude, coupled with his less than moral ways, earn Sima Yi the scorns of many, especially the Second and Seventh Enigma, and even his best friend Liaoyuan Huo, who believes a man of Sima Yi's genius should use his talents to save the people. Sima Yi, however, is not without an ideal of his own: if he's to choose a lord to serve, he would choose the strongest one, no matter how questionable that lord's principles are, to help him conquer the land and after that, takes over everything with a coup d'etat. When his clan was ruined under the hand of Cao Cao, Sima Yi finally resolved to make this scheme his life's goal, with the aid of his wife Shan Wu Ling and his estranged friend, Liaoyuan Huo. This will eventually culminate in the realization of his prophetic dream, shown at the beginning of the story: at the height of power as the Grand Preceptor Sima who usurped the throne of Cao Cao's descendants, he will be brutally killed by Liaoyuan Huo.

The 'feng' (鳳, lit. _phoenix_) of the series title (火鳳燎原, Huǒ Fèng Liáo Yuán, lit. _Fiery Phoenix Burns Steppes_ refers to Sima Yi. It's also noted that his appearance bears striking resemblance to the Fifth Enigma, Zhou Yu's.