How the hell do you guys call yourselves Ermac fans jeez...
Here's some history facts: He says "Onafa Nega Hor!"
Ermac was of course constructed by Shang Tsung & his design is reminiscent of a wizard(hood and all). In Assyrian culture (2500 BC to 605 BC), shamans would try to reanimate/create new life by attaching body parts together (the basis of the well known Frankenstein stories) and a prayer was said to bring the souls back to the material bodies and another was said to remove impure souls believed to cause decay. "Onafa Nega Hor" was the latter prayer and used in the context of Ermac's victory pose could signify a sort of purging of weaker souls.
Source: My brain, procrastinating at work, thinking of a cool bullshit back story. fuck knows what he says