Sergei "Sergo" Kovalski - a highly decorated ex russian special forces, who got into an accident during one of his missions and does not remember anything up until the point that he wakes up in Chernassus(even his name). Sergei has done very bad things in his past for his country and flashes of those memories are coming back in time. Sergo still remembers his combat and survival training. He is specialized is reconnaissance and demolition.
Before the outbreak: Sergei was involved in more than 30 different highly classified missions. During Sergei's last mission before retiring, he finds out that he is tasked with retrieving an experimental anti virus serum that might cure the outbreak. The mission was given to him by his Commander Boris Cvyatkov. Sergei and his team completes the mission, but Boris decides that they know too much of the conspiracy and murders all of them. Segei miraculously survives a shot in the head and wakes up in a hospital in Berezino after coma.
After the outbreak: Sergei wakes up and does not know anything about himself. He will only rely on his training to survive. Every player interaction will bring him closer to finding out who he is what happened to him. Eventually Sergei will get all his memory back and in the memory of his team, will begin the grand journey to find Boris and Kill him.