Making his debut in Ultimate Mortal Kombat 3, Ermac has been a controversial and mysterious character in the Mortal Kombat series whose existence was rumored since its inception. Ermac is a fusion of the many souls destroyed in Outworld's wars, only to be controlled by Emperor Shao Kahn and his Shadow Priests. Because of this, he refers to himself as "we", "our", "us", and "ours", instead of "I", "my" "me", and "mine". Because of the sheer concentration of souls within Ermac, he possesses the gifts of telekinesis, teleportation, and the ability to travel between realms.
Ermac rarely shows any signs of emotion, but he has proven to be quite wise and a very deadly combatant, using his telekinetic abilities to battle multiple opponents at once while keeping the upper hand. Disappearing after the events of Mortal Kombat Trilogy, he only returned in Mortal Kombat: Deception, where he was freed from Shao Kahn's grip by the blind swordsman Kenshi, whom he repaid by teaching him the Telekinetic Slam. He decided to become a force of good, partly in guilt of his past evils. To prove this, he decides to help Liu Kang free the souls of his friends from Onaga's control.
In the current timeline, this did not happen and, after the events of Mortal Kombat, he soon came under the possession of Shao Kahn's soul, as well as King Jerrod's. Despite this, it's implied that Ermac has free will and is no longer evil due to Shao Kahn's death, as he willingly chose to side with Kotal Kahn to be ruler of Outworld instead of Mileena in Mortal Kombat X, despite Shao Kahn's decree. While Ermac's goal has varied over time, his overall allegiance is to Outworld, whether from defending it from threats like Onaga or finding a proper ruler for the realm itself.