Reiko participated in the first Mortal Kombat tournament but was ultimately defeated by Shang Tsung himself in the very first battle. This was humilating for Reiko as this battle was only 5 minutes long and consisted of the elder man punching Reiko's face while Reiko was pinned to the ground. Reiko swore revenge as he was all bloody after the fight and returned to the Netherrealm. The worse part about the fight was that Shang Tsung only faught reiko to spite him. Later on in the tournement it was revealed that Shang Tsung was never even intended to join, but to simply host. This would mean that he really just wanted to humilate Reiko as they were supposed to be on the same side.
Later on Goro won the first tournement and became the champion of Mortal Kombat, it was a bad day for Earthrealm but also Reiko, still humilated by defeat. Reiko was a general of Shinnok's army but this did not concern Quan Chi, another sorcerer and friend of Shang Tsung. Quan Chi stabbed Reiko in the face when he returned to the Netherealm and carved a tattoo in his face, but it was a magic dagger that transferred energy, so Reiko didnt die from this.
Ten thousand years later Goro was defeated by Liu Kang in an honerable defeat and Reiko watched on with his blood boiling. "If I were the champion I would not have lost." He said to Shao Kahn.
"MAKE ME YOUR CHAMPION!" he demanded.
"I am your best soldier," said Reiko with confidence "you should behead Shang Tsung and Goro for their failures and leave the Earthrealmers to me."
Shao Kahn however didnt apperciate demands from his own servants, and banished him back to the Netherrealm (this is why Reiko did not appear until MK4). Reiko was not able to leave the Netherrealm until Shao Kahn's death in mk3, which allowed Reiko to finally exit hell through a teleporter.
Unfortunaetly, I am about to tell you what happened now after MK4. Shang Tsung found Reiko and learned of his escape from the Netherrealm, apparently Shinnok had returned, and Reiko was destined to lead the Netherealm army into an attack on Earthrealm. But after Shinnok's defeat, all of the demon soldiers Reiko gathered to take into battle disapeared.
Reiko was furious, Shinnok failed, Goro failed and even Shao Kahn failed. Shang Tsung was supposed to prevent failure in the Mortal Kombat tournement, "why would he ruin victory for Outworld just to humiliate me?" Reiko asked himself.
Reiko went to the Nexus and this is where a being called Damashi revealed itself as a glowing orange orb. But instead of decieving Reiko it told him of a truth so dark, so evil, that Reiko himself couldn't stand to listen any longer. The Deadly Alliance was using Reiko's hidden energy to ressurect the Dragon King's undefeatable army.
Reiko was furious, the Dragon King's army was his to control, not Shang Tsung's and certainly not Quan Chi! It was here that Reiko travelled to Shang Tsung's palace in a secret underground route. Reiko smiled to himself as he saw what appeared to be Shinnok's amulet on the floor, and as he went to grab it, the door behind him locked shut and he was trapped. It was just a fake copy and Reiko was deceived.
Reiko yelled out loud in shock as suddenly he came face to face with a giant blue Oni named Moloch. Moloch grabbed him by the legs and ripped them off, he then stomped on Reiko's head with his feet effectively crushing his skull.
Apperantly Quan Chi knew Reiko's every move ever since he carved the tattoo in Reiko's face. Shang Tsung came up with an idea on how to get rid of the warrior and his idea was entertaining Kano, who immediatly agreed to set forth the trap. Quan Chi laughed with his friends as they bonded over their treachery and that is why Reiko did not appear again until Armageddon where he was ressurected by Shinnok but he was again killed in battle this time by Shang Tsung himself. Shang Tsung sucked his soul out of his body without warning, Reiko was in the middle of fighting an Earthrealmer named "Stryker" when Shang Tsung got behind Reiko and stole his soul right from the back of his neck. Reiko then melted away on the battlefield in an agonizing death.
Ok so that was my silly story about Reiko, who was the main antagonist for a large portion of the Mortal Kombat X comics. I hope you guys enjoyed it and if you can, pick up MK4 cuz that was Reiko's first appearnce and he likely won't appear again.