Sima Yi (Legend Heroes)

Sima Yi is the most eminent of the Angels who oversee the Dream Battle and the main antagonist of the Korean Tokusatsu series Legend Heroes.

Initially appearing as a neutral observer, Sima Yi later becomes directly involved in the Dream Battle when he becomes the contract Angel of the Legend Hero Cao Cao. Though seeming to be an ally at first, Sima Yi is revealed as the true villain towards the end of the series, having been the real mastermind behind the experiments of Zhang Jue. He later becomes proactive in creating Dark Warlords and tricks his Warlord into letting him overtake him with the Angel Piece, transforming him into Overlord Sima Yan and allowing him to complete the final stage of his plan, to win the Dream Battle and use the Royal Seal to kill off the other Angels and become ruler of the Human World, with humans serving under him as his slaves.

History
Sima Yi was one of the Angels summoned by the Motherboard Computer to oversee the Dream Battle and distribute the Hero Pieces and Legend Changers to the chosen candidates. He is first seen observing Liu Bei defeat He Jin, noting that the first Legend Hero had been eliminated.

He would later give the Xiahou Dun and Xiahou Yuan Hero Pieces along with a Legend Changer to Cao Cao after he changed his name to be able to compete in the Dream Battle. During the Rainbow Event, Cao Cao participated and, after triumphing over all of the trials, selected Sima Yi to be his contract Angel. After Liu Bei unlocked Legend Hero Imperial and used its powers to defeat Dark Lu Bu, Sima Yi confronted Zhang Jue back at his workshop and killed the rogue Angel off, revealing himself as the one behind him. He later told Cao Cao that the Angels had a legend that the power of Legend Hero Imperial would destroy the Earth. Taking his Warlord to Zhang Jue's workshop, Sima Yi shows him the Dark Pentagon and convinces him to merge with it, saying that its power was the only thing that could be used to defeat Legend Hero Imperial. He also experimented with the creation of new Dark Warlords, turning two random humans into the Dark Warlords Xu Chu and Xu Huang as well as forcing Sun Shiangxiang to become the Dark Warlord Zhang Liao.

After the three new Dark Warlords were defeated by Liu Bei and Sun Ce, Sima Yi showed up to collect their Dark Hero Pieces, revealing himself as the true mastermind behind the Dark Warlords and Zhang Jue. He then reveals that Cao Cao has become Legend Hero Kaiser with the power of the Dark Pentagon and sends him to attack Liu Bei as Legend Hero Imperial. Kaiser easily triumphs over Imperial's powers and beats down Liu Bei and Sun Ce, causing the latter to succumb to his hidden illness and forcing them both to retreat.

After finding new hosts for the Dark Warlords, Sima Yi accompanies them and Cao Cao to the Red Cliffs Martial Arts competition to absorb Hero Power from its contestants. Liu Bei shows up to stop them but is unable to overcome Legend Hero Kaiser's power. Sun Qian then arrives and, having chosen to fight for his older brother while he is incapacitated, transforms into Legend Hero Taishi Ci and destroys all three of the Dark Warlords. He then fights Cao Cao but is unable to hold his own against the Kaiser's tremendous power and is forced out of his transformation. However, spurred on by Sun Qian's courage, Liu Bei transforms into Legend Hero Imperial and fights Cao Cao in a climactic battle, ultimately triumphing over the Kaiser, forcing the Dark Pentagon out of him and destroying it. With Cao Cao deprived of the Dark Pentagon's power, Sima Yi teleports them both back to his base of operations.

Sima Yi tells Cao Cao that the only other way for them to overcome Imperial would be for him to use one of the Angel Pieces to transfer his power to the Warlord at the cost of his own life. Deciding that the Angel Piece is the only possible way to defeat Imperial, Cao Cao agrees and allows Sima Yi to use it. However, the whole thing was a ruse for Sima Yi to overtake Cao Cao's body using it. Now in possession of Cao Cao, Sima Yi goes to defeat the remaining contestants in the Dream Battle and claim the Royal Seal for himself. Declaring himself to have been reborn into the Overlord Sima Yan, Sima Yi begins attacking civilians and absorbing their energy, turning them to stone. Liu Bei tries to stop him, but ends up having most of his energy drained too.

However, Mi Zhu and the Mi Zhu Brothers manage to tackle Sima Yan and take the other Angel Piece from him, tossing it to Zhuge Liang before Sima Yan turns them all to stone. Zhuge Liang then uses the Angel Piece to restore Liu Bei and power him up at the cost of his own life. With enough power to stand comparably to the Overlord, Liu Bei goes to confront him. He attempts to convince Cao Cao to stand up to Sima Yi and reject him from his body, reminding him of Wang Yun and his duties as a police officer. Diaochan also shows up, brought there by Cao Cao's Hero Pieces, and also pleads with Cao Cao to snap out of it. As he begins to lose controls, Sima Yan attempts to kill Diaochan by firing an attack at her, but the attack is blocked by Li Jue and Guo Si at the cost of their Legend Changers, causing them to be eliminated from the Dream Battle.

Spurred on by Diaochan and Liu Bei, Cao Cao overpowers Sima Yi and expels him from his body. Furious that he can now no longer obtain the Royal Seal, Sima Yi summons Legend King Deathlon for him to pilot and destroy the world with out of spite. In response, Liu Bei, Cao Cao and Sun Quan all summon their mechas and combine them into Legend King Eternity to engage Sima Yi in a final Final Battle. After a tough a climactic battle, the three destroy Deathlon and kill Sima Yi, causing the evil Angel to explode in a burst of dark energy.