A former Soviet Army colonel and Umbrella executive utterly loyal to Spencer. Although Sergei originally worked in the underground laboratory beneath Raccoon City developing T-A.L.O.S., he later transferred to Umbrella's Caucasus laboratory in Russia. The supercomputer he took with him, which contained a vast amount of Umbrella's research and other data, was eventually targeted by Wesker. Sergei went up against him by willingly mutating into a creature, but he was ultimately defeated—yet another victim of Wesker's nefarious plans.
The B.O.W. below is Sergei's "old friend," the Ivan. While they were developed as T-Virus Tyrants, their highly protective white coats and distinctive visors are quite different compared to the classic Tyrant design—although their coats are reminiscent of the one that the T-103 Tyrant from RE2 wore.