Dark Reflection

The Doppelganger is a vicious creature, created by machines old as time itself, hidden deep within the earth.
It has a mind of his own and can act on it's own, giving it the ability to adapt to certain unforeseen circumstances. However there is a word in an ancient language, one only Jack knows, to control it. As soon as you say the word the Doppelganger has to obey you - whatever the order might be.
The Doppelganger has all the abilities of Nate and beyond, he is superior in every way, making him a deadly opponent.
Though considered little less than a walking weapon there is something in the dark eyes of the creature which might be a hint of an on consciousness. And own plans.