Smoke is a ninja of the Lin Kuei and Sub-Zero's friend. Both did'nt want to be robots. Sub-Zero escaped, but Smoke didn't. He discovered he still have a soul and decided to help Sub-Zero.
Origin: Mortal Kombat 3 and Mortal Kombat 2
Smoke defeats Shao Kahn and saves the world, but he is trapped in his robotic body.