In life, when Bi-Han was Sub-Zero, he was credited as the most cunning thief and assassin of the Lin Kuei. Some time ago, he and his clan were hired by the Netherrealm sorcerer Quan Chi to retrieve an ancient scroll in a Shaolin temple. However, unknown to Sub-Zero, Quan Chi also hired the Japanese ninja, Hanzo Hasashi - codename Scorpion - of the Shirai Ryu clan, and the Lin Kuei's ancient rivals, for the same task in case Sub-Zero failed.
Sub-Zero fought past the Shaolin monks and obstacles guarding the temple where the scroll was held. Upon arriving at the chamber where the scroll was contained, Sub-Zero encountered Scorpion. A violent battle for the map ensued with Sub-Zero as the victor and coldly, savagely killing Scorpion. Sub-Zero escaped with the scroll.
Sub-Zero returned to the Lin Kuei mountain fortress with the scroll. As compensation, Quan Chi made good on his promise to the Lin Kuei Grandmaster, as well as the absolute and utter destruction of the Shirai Ryu. Quan Chi also revealed his hiring of Scorpion - something that didn't settle well with Sub-Zero.
Quan Chi revealed that the scroll was a map that showed the way to the legendary Temple of Elementals. Concealed inside was an amulet that was said to contain great mystic powers. Quan Chi, having crossed the gods of Earthrealm in the past, was sealed from entering the temple. Thus, Sub-Zero was dispatched to retrieve the amulet. From the moment he arrived, Sub-Zero faced incredible danger from lethal traps and elite guards. The temple was also protected by four elemental guardians including Fujin, a god who would play a future role in the events to come. Sub-Zero, however, in addition to possessing mastery over cold, was among the most cunning and powerful warriors in Earthrealm. Neither the temple's obstacles, nor the guardians were able to stop him. With the defeat of the last temple guardian, in the chamber containing the amulet, the mystic seal thwarting Quan Chi from entering was lifted. As Sub-Zero was about to retrieve the amulet, Quan Chi mystically materialized and took hold of it. He revealed the true nature of the amulet: it had belonged to Shinnok, a fallen Elder God who was banished to the Netherrealm millenia ago for attempting to conquer all of creation.
Quan Chi vanished, and Sub-Zero stood in the chamber alone. Moments later, Raiden, the god of thunder and protector of Earthrealm, appeared. Displeased with Sub-Zero and his clan's greed and ignorance, Raiden commanded Sub-Zero to recover the amulet, as the god had no dominion there. Conjuring a portal, Raiden sent Sub-Zero to the Netherrealm.
Sub-Zero arrived and was immediately trapped in the Prison of Souls by Quan Chi's guards. There, he was met by the undead spectre of his archnemsis, Scorpion, who blamed Sub-Zero for the destruction of his clan and family. Although Scorpion couldn't die, he was beaten by Sub-Zero and forced to retreat. Sub-Zero escaped and fought Quan Chi's underlings: Kia, Sareena, and Jataaka. He killed Kia and Jataaka, but strangely spared Sareena. Retrieving their transportation crystals, he was able to get to Quan Chi's fortress and confronted the deceiving sorcerer.
Quan Chi then revealed to Sub-Zero that the only reason he was able to retain his mortality in the Netherrealm was because of the evil in his heart from being the ruthless assassin he had been known as. Sub-Zero fought the sorcerer; although he was the clear victor, Sareena suddenly appeared and helped Sub-Zero defeat her master. She then begged Sub-Zero to take her away from the Netherrealm, but she was quickly killed by Shinnok, who was now powered by his amulet (unknown to the god, Quan Chi had actually given him a fake, keeping the real amulet for himself). Using his cunning, Sub-Zero grabbed the amulet from Shinnok, who then morphed into a giant demon. It is unknown if Sub-Zero escaped or fought the demonic Shinnok; either way, Sub-Zero escaped through a portal created by Raiden, and delivered the amulet to the god.
When Sub-Zero questioned what Quan Chi said to him, Raiden confirmed it, but reminded the warrior that only he could change his own fate. It was up to Sub-Zero to choose his destiny, but were he to die with his soul thus corrupted, he would descend to the Fifth Plane of the Netherrealm to face a terrible fate unknown even to Raiden.
Upon returning to the Lin Kuei headquarters, he learned that he had been invited to the Mortal Kombat tournament by Shang Tsung himself. The Lin Kuei had previously been approached with a contract for the sorcerer's head. Sub-Zero would accept the invitation, with his ultimate designs being set on assassinating Tsung.
To this day, the particulars of Sub-Zero's fate during the tournament remain largely unknown. By Raiden's account, Scorpion had also participated in the tournament and swore to Sub-Zero that he would get his revenge. Sometime after the defeats of Goro and Shang Tsung by the White Lotus monk Liu Kang, and the island's subsequent eruption into chaos, Scorpion confronted Sub-Zero at the island's gates and challenged him to a fight to the death. Fueled by vengeance and the demon energies of the Netherrealm, Scorpion burned Sub-Zero to death.
True to what Raiden had predicted, Sub-Zero's soul descended deep into the Netherrealm's Fifth Plane, where he would become a demonic form of what he used to be. He would be given the name of Noob Saibot.
Saibot would become a member of the Brotherhood of the Shadow, the very thing he had resisted becoming whilst alive. In a darkly ironic twist, Saibot would now pledge allegiance and loyalty to Shinnok. One of his first tasks for his new lord would be to observe and report on the events taking place on Earthrealm and Outworld; to this end, he remained in the shadows during the Outworld tournament, faithfully monitoring the situation for the fallen Elder God.
At Shinnok's behest, Saibot aligned himself with Outworld's emperor, Shao Kahn, during Kahn's invasion of Earth. It is unknown of his role in the battle.
After Kahn was defeated, Shinnok, sensing his time had come, was freed from the Netherrealm by Quan Chi, and conquered Edenia. Saibot now served his overlord directly. But despite the Elder God's careful planning, Shinnok was once again defeated by Raiden's forces and the Brotherhood of the Shadow was disbanded. With Shinnok defeated utterly (Saibot later refers to him as simply "gone"), Saibot returned to the service of the still-weakened Shao Kahn.
A few years later, he appeared during a battle between the armies of Edenia and the Shokan (led by Kitana and Goro) with the Outworld army (lead by Kano). He attacked an exhausted Goro, mortally wounding him. The war ground was then lead to a stalemate.
With Kahn having been thought slain at the hands of the Deadly Alliance and Shinnok vanquished, Saibot slowly changed from a pawn into a player. Free to pursue his own interests, and uninterested in the affairs concerning the rise of Onaga, he plotted to create his own legion of assassins. While searching Kahn's abandoned fortress, he discovered the inert body of Smoke. Reprogramming the cyborg to remain loyal to him, he reactivated his nanotechnology, and formed plans to create an army of cyber-demons, using Smoke as a template. Their team was Noob-Smoke.
He was then seen leaving Shao Kahn's fortress with Smoke by his brother, Sub-Zero, and Sareena. Saibot and Smoke disappeared into the Netherrealm. Sub-Zero ventured after the two. However, Saibot and Smoke knew they were being followed and attacked Sub-Zero in the Netherrealm (It was then that Sub-Zero revealed Saibot to be his older brother). It appeared the grandmaster was overpowered and doomed until Sareena jumped in, fending off Sub-Zero’s would-be assassins but not before Sub-Zero was left unconscious, and upon waking, Sareena had reverted back to her demonic form. Dazed and still very confused, Sub-Zero attacked and Sareena fled to the depths of the Netherrealm.
There she was ambushed by Noob, Smoke, and her former master, Quan Chi. The sorcerer knew of her allegiance to Sub-Zero and demanded to know the location of the Lin Kuei temple.
Saibot was no longer teamed with Smoke intrinsically, though they did work together in leading an invasion of the Lin Kuei temple in order to retake the clan and find and kill his brother, a plot which the Edenian warrior Taven helped foil. Sub-Zero then began to work on cleansing his brother's soul.