Sergei is an officer in Umbrella. During his army days, he held the rank of colonel and is still called that on occasion as a nickname. He approached Umbrella after the fall of the Soviet Union, looking for work. He is involved in Tyrant research, and his experience in military affairs made him instrumental in the founding of Umbrella's private militia, the Umbrella Biohazard Countermeasure Service (U.B.C.S.). Nicholai Ginovaef is one of his subordinates.
He shows an ardor for following Ozwell E. Spencer's orders and makes sure even the most radical of Spencer's wishes are carried out.
As an individual with a rare genetic makeup, Sergei became the model for the majority of Umbrella's Tyrant program, beyond the T-001 and T-002 projects initiated by the team led by Albert Wesker and William Birkin. So that Umbrella could produce more Tyrants, Sergei allowed them to make ten clones of himself. He also ordered the re-engineering of two T-103 Tyrants in order to produce his personal bodyguards, known as "Ivan".
On Spencer's orders, Sergei was personally involved in the events surrounding the outbreak in Raccoon City. At the Arklay Training Facility, Sergei dispatched one of his "Ivan" Tyrants to kill Albert Wesker for failing to save the facility from James Marcus' attack. At the Spencer Mansion, he was tasked with recovering the TALOS prototype, which eventually became one of Umbrella's most impressive bio-organic weapons. When Raccoon City itself was overrun, Sergei recovered the Red Queen data core from Umbrella's laboratory, allowing the company to recover from the loss of their Raccoon installations.
After Umbrella was forced to go underground, Sergei was put in charge of Umbrella's new base of operations in the Caucasus region of southern Russia. In 2003, this stronghold came under attack by troops led by Chris Redfield and Jill Valentine. Despite unleashing the most powerful bio-organic weapons that Umbrella had to offer, including TALOS, Sergei was unable to repel the assault. He ultimately met his end at the hands of Albert Wesker, who had also infiltrated the facility.
Sergei's weapons of choice are a double-ended blade (with which he often cuts himself deliberately) and a Mauser C96 pistol, which he fires at Wesker in one cutscene.