Onaga originally formed the greatest army that Outworld had ever known; an army so powerful that it had never lost a battle. When he was betrayed and killed by Shao Kahn, his army was entombed along with him after they ritualistically committed mass suicide after his death.
For millennia, this army of undead warriors would remain undiscovered in his tomb and awaiting his second coming, until centuries later, the sorcerer Quan Chi discovered their location after escaping from the Netherrealm, and along with the help of another sorcerer Shang Tsung was able to revive them one by one. The young fighter Li Mei with the intention of freeing her home village, entered the Mortal Kombat tournament held by the Deadly Alliance, only to discover that the tournament itself was a setup; the Deadly Alliance was planning to transplant the winner's spirit as the last soul needed to completely revive the Dragon King's lost army.
Before Li Mei’s soul was completely transferred, her teacher Master Bo' Rai Cho rescued her, yet the experience left some strange and strong supernatural influence on Li Mei. The Dragon King's army was completely destroyed in an ethereal energy blast caused by the thunder god Raiden's suicide, but their master Onaga, who had risen from beyond the grave, survived the explosion and continued forward to reclaiming Outworld, achieve his revenge and complete his plan of conquering the realms with the aid of a set of certain treasures with powers beyond comprehension.
After Onaga's return and eventual defeat, it was revealed that the army was only undefeatable due to his ability to constantly resurrect them after their death during battle.
- The Dragon King's Army seems to be loosely based on the Terracotta Army.
- In the production gallery of Mortal Kombat: Deception, there exists a character called the Undead General, who is part of the Dragon King's Army, and is an obedient servant to Onaga himself.