Reptile comes from a peaceful race of reptiles which inhabit a dark corner of the Outworld. His people possessed great strength, as well as other abilities which made them natural warriors. To them, though, their abilities were a curse, as they were often forced into military duty by the Outworld rulers. In modern times, their number had dwindled to a mere handful. Reptile found employment in the palace of Shao Kahn, the ruler of the Outworld. Five hundered years ago, Reptile was assigned to be Shang Tsung's bodyguard when the evil sorceror took control of the Mortal Kombat tournament. He served faithfully, remaining in the shadows until Tsung met defeat at the hands of Liu Kang. Reptile and Shang Tsung were forced to flee back to ther Outworld in utter defeat.
Upon his arrival in the Outworld, Reptile became aware of Tsung's plot to enslave the remaining members of Reptile's race. Outraged, he entered the second Mortal Kombat to gain revenge on Tsung. He was unable to kill Tsung, and instead returned home to defend his people. Unfortunately, he discovered that they had all died since he had left. His only wish was for his people to continue their peaceful existance, but now that was impossible. He returned to Shao Kahn in the hopes that the emperor could somehow revive his now extinct race.
After Kahn began his invasion of the Earth, Reptile and Jade were assigned to track down the renegade Princess Kitana. Reptile was given orders to assassinate the princess, but Jade believed that it was a simple retreeval mission. Reptile's excellent tracking senses allowed them to locate Kitana's hideout on the Earth realm, and he attacked her. When Jade realized his true intent, she sided with Kitana and Reptile was defeated. He returned to Shao Kahn in disgrace, only to find that Kahn now had no intention of ressurrecting Reptile's people. Angered at having been crossed once again, Reptile began to exterminate other races just as his own had been wiped out.
His crimes soon caught up with him, and he was banished to the Neatherrealm for his acts of genocide. He allied himself with Shinnok, a fallen Elder god of great power. A general in Shinnok's army of darkness, he led his troops to victory in the Outworld. He believed that his actions would merit the resurrection of his race, and he approached Shinnok's sorceror Quan Chi about this matter. Quan Chi declined to help Reptile, and when the warrior attacked him Shinnok intervened. The Elder god executed Reptile for his affront, making Reptile's race truly extinct.