Sima Yi is a reputed intellectual who is accredited as the ancestral founder of Western Jin. Once he agreed to serve the Cao family, he became one of Cao Pi's close friends and subsequently an influential figure in Wei, cunningly defending himself from his many detractors. Cao Cao suspected that Sima Yi would never be satisfied serving under another, an opinion which would ring true years later when the Sima family reigned supreme after his death. Romance of the Three Kingdoms and the dubiously accurate Hanjin Chunqiu depicts him as a conniving individual who was intimidated and infuriated by Zhuge Liang's sagacity. His wife in DW & later EX Wife in BLAD is Zhang Chunhua; Sima Shi and Sima Zhao are his eldest sons.
In Beyond Light and Darkness, He Joined Dark Emperor upon learning of his quest for Domination. He is one of the Primary Antagonists of the Series of BLAD and also one of Terrantos's Head Strategists and Leader of the Elite Group, Shadow Minds a group dedicated to strategy within Shadowblood.
Originally introduced as a calm and gloomy strategist, Sima Yi eventually became a man who is more arrogant and conniving. He is known for his maniacal laughter and insulting friend and foe alike as "Fool!" or "Imbecile!" He doesn't truly believe in Cao Cao but is always eager to exploit every opportunity given to him. Prideful of his intellect and believing that he has an unsurpassed wit, he regards Zhuge Liang as a worthy opponent.
While usually known to be contemptuous and seemingly shallow, Sima Yi can also be easily humiliated when he can't predict the results of his actions. This mainly occurs during the spin-off titles in the Dynasty Warriors series, such as the mahjong title and Dynasty Warriors 6: Empires. Recent titles has him display this feature openly with Wang Yi or Wang Yuanji, since both women easily see through him.
He trusts Zhang He's versatility for his plans and relies on him during the later parts of the Three Kingdoms period. In recent titles, he shares a loosely trusted partnership with Cao Pi and the heir refers to him by his style name. Sima Yi is fascinated with Cao Pi's abilities and generally finds him a better ruler than his father. In the Warriors Orochi series, he offers special praise for Sakon, Kojirō, Mitsuhide, and Kiyomori. Sima Yi treats Masamune, Da Ji, and Yoshihiro as his crossover rivals.
In Beyond Light and Darkness, Sima Yi seems to be alright serving Under the Dark Emperor to a point he shows great loyalty and respect to the Emperor of Darkness. Sima Yi is Hellbent on making Dark Emperor's goals a reality so much he is not put aside his own rivarly with his Old Enemy, Zhuge Liang to form strategies that will put Godstrike into a corner. Sima Yi now seeks not just to conquer the land of Dynasty Warriors under Jin but under the power of Jin, Wei, Shu, and Wu so Dark Emperor has control over the entire Land.
Sima Yi has shown to be a Master Manipulator as well if not already, he has manipulated many of his "idiotic Imbeciles" for enemies feelings and beliefs to his advantage such as he used Natsu's feelings for Lisanna against him, as Sima Yi used dark magic to create a Lisanna which caused Natsu not able to fight, this giving him the perfect Opportunity to attack Natsu. Sima Yi enjoys toying with people's heads and feelings viewing such things as things of a Fool, unless its himself, his comrades, or even his Master. He views everyone as a pawn in Dark Emperor's grand schemes and will use his enemies as well as known traitors to his advantage.
Sima Yi seems to hate Ganondorf and Sephiroth above everyone else, he uses thier feeble attempts or "secret plan" to overthrow the Dark Emperor to his advantage, as Sima Yi pretended he was going to overthrow the Dark Emperor and so he performed an "Alliance" with these two but even told them of his plan to rid themselves of thier enemies only to lead them into a trap surrounded by the Jin and Wei Armies led by himself and Cao Cao. When Ganondorf questioned him why he betrayed them (Ganondorf and Sephiroth), Sima Yi says "Your Greatest Crime was not the fact you thought I would help you. Your Greatest crime is that you foolishly thought you had the right to think I would and to overthrow Our Lord....So Now Die".
Sima Yi is also one of Terrantos's Head Strategists along with his Former Enemy, Zhuge Liang (who was a spy of Godstrike). One of Sima Yi's plans to help Terrantos's influence grow was for him to have a Maiden from each of the Dynasties: Jin, Wei, Wu, and Shu. Zhuge Liang agreed with Sima Yi on this, So Sima Yi instructed Liu Bei, Cao Cao, and Sun Jian to pick one of the women from thier empires to be a Mistress to thier Dark Lord and Master. Sima Yi coldy asked his Son if he could wiped his marriage away with Yuanji but Surprisingly Sima Zhao agreed. Sima Yi than diabolically laugh as he wiped that out of him thus Zhao and Yuanji forgot everything about that and that they ever had a Son.
Soon Sima Yi presented to his Master Wang Yuanji of Jin as a Mistress, and his 3 cohorts offered a Mistress to thier Master as well. Wang Yi of Wei, Xing Cai of Shu, and Shang Xiang of Wu. This Caused Sima Yi's plan to come to fruition for his Master, as his Cold Yet calculating plan was able to cause everyone in the Dynasty Warriors universe to fear the Dark Emperor as he was not just the Ruler of Shadowblood but part of the 4 Kingdoms due to this, causing everyone to fear his Power and Intellect. Sima Yi than decided to corrupt the land of Samurai Warriors with the Help of Oda Nobunaga and soon he was able to gain More Troops for the Dark Emperor, including Kotaro Fuma. Sima Yi shown a sign of delight and madness because of this and thus he started calling himself "The Mad Emperor".
These 2 Plans Later gained Sima Yi the Name "Emperor of Jin" as well as the Name "The Cold-Hearted Demon from Hell".
Sima Yi is a scholar who thoroughly believes in his intellect. He appears sometime after Chi Bi (Guan Du in Dynasty Warriors 3 if playing as him) as the master strategist of Wei. After Cao Cao's death, he is often depicted as the leader for Wei and appears in many of the series's decisive battles. He stars in Zhuge Liang's Northern Campaigns, and he is known in most titles to see through Ma Su's plot at Jie Ting. He also correctly reads the sign of his rival's death at Wu Zhang Plains and orders the army to charge. Depending on the title, he may then live to suppress the remnants of Shu and Wu.
His Legend Mode in Dynasty Warriors 4: Xtreme Legends takes place at Mount Qi. Thinking that Wei Yan will feed him with inside information, Sima Yi is led into one of Zhuge Liang's traps. Surrounded by archers and trapped in a fire attack, he is saved by rainfall. With the heavens on his side, he fights his way through perilous odds, which forces Zhuge Liang to issue an all-out attack. Slaying the Shu generals, Sima Yi is able to escape safely.
In Dynasty Warriors 5, Sima Yi was born from a prestigious family and studied his life to become a renowned scholar. Summoned by Cao Cao to join Wei, Sima Yi demonstrates his skills as main strategist at Fan Castle and ask Wu for reinforcements. He serves Cao Pi after his liege's demise and kills Ma Su at Jie Ting. During the conflict, he meets Zhuge Liang and deems the Prime Minister to be his greatest threat. However, when his rival perishes at Wu Zhang Plains, he fears nothing while he crushes the other two kingdoms. With Wei as the land's ruler, it's implied that he plans to overthrow his master in due time.
His Legend Mode in the Xtreme Legends expansion pairs him with Cao Pi and Xu Huang. The trio work together to punish the traitor, Meng Da, at Xin Castle. While he holds himself within the castle's walls, he forces several Wei generals to fight their master. Sima Yi notes their weakened resolve and orders his allies to spark mutiny among Meng Da's troops. Striking the final blow against Meng Da, the defector accuses Sima Yi for false loyalties before he dies. The strategist replies that he is only biding his time.
Cao Cao summons for Sima Yi's talents before the Battle of Chi Bi in Dynasty Warriors 6. Originally bored and unimpressed by the land's chaos, he becomes fascinated by Zhuge Liang's tactics and his experience in battle. As he spends more time with his master, Sima Yi begins to form his own ambitions and image for the land. Consumed with his inner desires, he loses interest with his rival and works to destroy the other two kingdoms. Although ordered to keep watch in Han Zhong for rebellion, Sima Yi stages a coup d'état at Xu Chang with Zhang He and others. Upon murdering Cao Cao, his lord expresses his wishes to make a land for the people with his dying breath. Sima Yi, though acting uninterested, complies with his master's ideals to an extent during his rule.
Dynasty Warriors 7 has Sima Yi appear as a minor character during the Three Kingdoms Story Modes as a supporter for Wei. During Wei's story, he appears as a strategist for Cao Cao during the conquest for Han Zhong. Feeling no remorse for Xiahou Yuan's death, he oversees the alliance with Sun Quan for the sake of slaying Guan Yu. He acts as the main commander at Fan Castle, directing Xiahou Dun's set of objectives on the field. During Shu's Story Mode, he appears as the commander at Wu Zhang Plains. Sima Yi also joins the defense at Dong Kou in Wu's Story Mode.
In Jin's Story Mode, he begins as Wei's Grand Commander. Shu, Wu, and Wei have lost many heroes due to the war, and their conflicts have lead to an uneasy stalemate. Sima Yi feels the land has become worse than before due to people constantly repeating the same tiring mistakes, deepening the warfare that continues to plague the land. He feels his talents should be used to attend to the wavering situation, but his duty instead dictates he attends to fruitless internal rebellions. Frustrated by witnessing generals act in the endless monotony, he spares no mercy to Gongsun Yuan or Wang Jian when they attempt to plead for forgiveness, having them executed for their crimes. Reminiscing of his past battles with Shu, he realizes that Zhuge Liang was the only man worthy to face his intelligence. With his rival gone, Sima Yi feels his role in the wars are futile and withdraws his support for the current Wei emperor, Cao Fang. His retreat from politics allows Cao Shuang, Cao Fang's other influential supporter, to gain prominence in the court. When Cao Shuang orders a half-cocked invasion in Shu, Sima Yi entrusts his son, Sima Zhao, to stop it in its tracks. His son's stunning performance and Cao Shuang's incompetence to try to deal with rumors of Jiang Wei's invasion led to his family gaining a better reputation with those in Wei.
Coping with the fact that there are none living in the world who can match his intelligence, Sima Yi decides that it's his new goal to at least end the cycle of stupidity he despises. After Sima Shi reports that his father is suffering from an illness that doesn't allow for visitors, Sima Yi decides to use this opportunity to kill Cao Shuang. Abhorring Cao Shuang's selfish desires and petty excuses for Wei's future, he has the Grand Commander executed and reclaims his title. Not soon afterwards, Sima Yi and his sons march out to deal with Jiang Wei's invasion at Mt. Niu Tou. They return to learn of Wang Ling scheming with Wu in an attempt to lower the Sima family's favor to Cao Fang. Sima Yi leads his family to quickly deal with the threat and repels Wu's attempted invasions. Their efforts further instill the Sima family's reputation as an unshakable pedestal in Wei. The constant string of battles take their toll on his body, finally making Sima Yi bedridden with the illness he stubbornly kept hidden from his family. After he passes on the right to lead the family to Sima Shi, Sima Yi dies.
His first Legendary Mode lets players control his side of Wu Zhang Plains present in Shu's Story Mode. Sima Yi's second Legendary Mode has him pit a contest between his family and the entire Zhuge family to prove who has the heftiest brainpower between them.
In the first game, Sima Yi serves Orochi faithfully, gladly breaking his bonds with Wei. He can join the Samurai forces during one of their gaiden stages. If the player successfully executes the two fleeing officers, therefore ruining Sima Yi's trap, he will be in awe of the coalition's genius and joins their cause.
Warriors Orochi 2 has Sima Yi first working for Masamune's army. During the Samurai storyline, he faces the Sakon's forces at Chang Ban and is outwitted by Shingen. Impressed by Shingen's tactics, he decides to accompany them. In other faction story modes, he will survive to serve Orochi X. His dream stage teams him with Mitsunari and Masamune. The trio unite their strategies at Xia Pi to drive the coalition back.
Sima Yi is first seen in the past in Warriors Orochi 3. He and Cao Pi once led an army of followers to surround and defeat Da Ji at Tong Gate. Driven back by the coalition, his faction is later seen spearheading an attack against the serpent army at Hulao Gate. Reinforced by Cao Cao and Sima Zhao in the changed future, their skirmish proves successful and the coalition obtains the firepower they need to slay Hydra.
As a member of the coalition in the future, he and Masamune seek to investigate a strange rumor of a "girl within a box" within the Yellow Turbans' possession. Their search leads to Gracia and Zhang Jiao joining humanity's cause. He also assists the coalition in locating Guo Jia's whereabouts in the past. Later Sima Yi and his entourage return to the past to search for Wang Yi, an acquaintance whose talents on the battlefield perks his interest for her recruitment. Although she is ashamed by her revenge marring his trust in her, Sima Yi is still adamant in his acceptance for her.
Sima Yi is a confident and talented magician for Wei in Kessen II. He serves as a strategist and adviser for Cao Cao. He is first seen strutting into Cao Cao's throne room midway through the game, wondering why he can't find the "great hero of the land". He bluntly ventures that Cao Cao is the cause of the land's natural disasters as they continue due to the conqueror's selfish desires. He states that the lord will lose to Liu Bei if this continues, which gets an angered response from Cao Cao. Sword drawn to the offender, he growls for his name to which Sima Yi politely bows and introduces himself. Cao Cao likes the sorcerer's fearless nature and recruits him on the spot. His battle strategy is one of the best ways to fend off an angry Ma Chao.
Sima Yi began his career as Secretary of Literature under Lord Cao after the pacification of the north. His first military assignment was against Zhang Lu in Hanzhong. Sima Yi’s strategies were a success and Lord Cao was greatly impressed.
After Cao Cao, and his son, Cao Pi passed away and Cao Rui stepped up to the throne, Zhuge Liang started his expeditions to the north. In 227, Meng Da attempted to defect back to Shu. After hearing this, Cao Rui sent Sima Yi to Xincheng to stop Meng Da from defecting. The battle killed Meng Da in the process and Sima Yi was given much praise. Starting from the year 228, Cao Zhen led the defense against Zhuge Liang while Sima Yi led the strategies for the battles.
In the year 230, Cao Zhen passed away and Sima Yi took command against Zhuge Liang. Also in 231, Sima Yi finally faced Zhuge Liang's armies in battle. Sima Yi was mocked by his generals during the battle for not facing Zhuge Liang's men directly in battle. Furious, Sima Yi sent his men but was defeated easily. Sima Yi didn't falter and waited for Zhuge Liang to retreat. Indeed, Zhuge Liang retreated due to lack of supplies and Zhang He was sent by Sima Yi but was killed at Mumen Trail after being ambushed by Zhuge Liang's men.
In 234, Zhuge Liang began his final expedition to the north and met Sima Yi's men at Wuzhang Plains. During this time, Zhuge Liang sent a message to Sun Quan to attack Hefei in which Sun Qun accepted. Zhuge Liang attempted to force Sima Yi out of the Wei's main camp but none of the attempts worked. Sima Yi's men were getting impatient and Sima Yi requested to Cao Rui to engage the Shu forces. In response, Cao Rui sent one of his strategists, Xin Pi, to tell them to be patient. In time Sima Yi sensed that Zhuge Liang wouldn't live long due his rival's attempts of forcing him out of the camp. Sun Quan was defeated at Hefei due to a mysterious plague causing his men to fell to illness. Wu's defeat caused Zhuge Liang stress and fell to illness in Autumn 234 and died weeks later.
Sima Yi sensed his rivals death and quickly attacked the Shu's Forces. Even though they were quickly charging to the Shu's main camp, Sima Yi felt that Zhuge Liang's death was fake and ordered his men to go back to camp and Shu retreated safely.
During the Reign of Cao Fang; Sima Yi was appointed as Prime Minister and received the Nine Dignities from Cao Fang. Sima Yi placed his sons Zhao and Shi in high positions and took away power or killed anyone who still supported the Cao Family. Also duing Fang's reign, Sima Yi started a rebellion which caused Wei's regent, Cao Shuang, to step down. Sima Yi took position as regent later on and his sons, after his death, gave high contributions to Wei including Shu's fall during Sima Zhao's reign in 263.
As regent, he quelled a rebellion led by Wang Ling assisted by Wu at Shouchun. After the long battle, Sima Yi fell ill and Sima Shi became his heir to his position.
Sima Yi died in 251 AD and was succeeded by son, Sima Shi. Fourteen years later, his Grandson, Sima Yan, usurped the throne and established the Jin Dynasty.