Dr. Friedrich Steiner is Viktor Reznov's target in Black Ops as well as Alex Mason's target. Steiner also created the toxic Nova 6 gas, which was sought after by the Germans, Russians, and British during and after WWII.
Black Ops Universe
During the late 1930s, Steiner accidentally mixed noxious chemicals together and flooded his labs with a horrible chemical which he later dubbed "Nova 6". The gas was uncontrollable unless contained.
Hitler soon came to power and ordered large shipments of Nova 6 to be used as chemical warfare. The ship carrying the cargo got trapped in the ice and everyone aboard suffered. The Nova 6 never made it to its target.
After WWII, two Russian leaders--Dragovich and Kravchenko--sent out a search party to find Steiner and take the Nova 6 cago out of the ice. The party found Steiner and the ship before going aboard to find the canisters of Nova 6. Dragovich and Kravchenko were not convinced that the gas really worked, so they forced their men into two chambers to test the gas. Before both chambers were filled with gas, British troops attacked the ship and attempted to kill the two Russians and Steiner but failed when they escaped. Only Viktor Reznov and another Russian escaped the ship alive, blowing up the ship so no country could possess the Six. (This level is playable in Black Ops.)
20 years later, Steiner, Dragovich, and Kravchenko are still obsessed with obtaining the Six. Draovich hires Dr. Daniel Clarke to finish a batch of Six which was produced by Steiner. Clarke finishes his work and is then hunted down by Dragovich's men to eliminate all loose ends. Clarke is shot in the head just as important information on the Numbers are about to be revealed to Agent Jason Hudson. (Payable in Black Ops.) Steiner is also hunted done by Dragovich's men, but is killed by Alex Mason before the Numbers information is revealed. (Also playable in Black Ops.)
Friedrich Steiner was a doctor at Vorkuta during WWII hired by Dragovich and Kravchenko. He created the Six as mentioned earlier but also experimented on prisoners. The experiments were a hope to create someone who could decode the Numbers if needed. Years later, the experiments prove successful as Mason (who was an experiment) unlocks the sequence.
Steiner worked briefly with Group 935 while trying to create the ultimate soldier.
He later stole equipment from Der Riese after the zombie outbreak. While presenting the stolen items at a conference, he spilled Nova 6 gas and created the Crawler Zombies. He may have also created Phasing Zombies by teleporting Crawler Zombies by mistake.