First appearing in Mortal Kombat 4, Reiko is one of the most mysterious characters in the Mortal Kombat universe. He is a grim and menacing looking man with black and white hair, glowing eyes, and a black mask-like tattoo on his face.

Very little is known about him, except that he is a merciless and brutal general. He has always fought alongside the Forces of Darkness, serving as a general for both Shinnok and Shao Kahn. Reiko is also a member of the Brotherhood of Shadow. He aided Shinnok in his war against the Elder Gods, and was thought to have been killed. Reiko returned during Mortal Kombat 4, but with Shinnok's defeat, he disappeared again. Reiko eventually joined Shao Kahn's army, and through his cruelty and ruthlessness in kombat he earned the position as general.

Reiko's ultimate goal is to replace Shao Kahn as emperor of Outworld. In addition to wearing similar armor to Kahn, it is revealed in Mortal Kombat Deception that he likes to sneak into Shao Kahn's throne room and wear his helmet. Reiko has also claimed that he will one day rule Outworld.

In Mortal Kombat: Armageddon's Konquest mode it is revealed that Reiko has an intense hatred for Quan Chi, but the reason for this hatred is unknown. Reiko asks Taven to join Shao Kahn's army, but Taven refuses, stating that he must find and kill Quan Chi. Reiko likes the idea, but he had been ordered to protect Shao Kahn's allies, including Quan Chi. The two battle, and Reiko is defeated.

In Reiko's Armageddon ending, the godlike power of Blaze surges through his body, making him more powerful than even Shao Kahn. Reiko kills Shao Kahn and claims his helmet. As he places the helmet on his head, it fuses to him, turning him into an incredibly powerful and savage warlord.