Adder

From Resident Evil Wiki

A snake that was not mutated extensively by the T-Virus. These snakes are not part of Umbrella's research, but rather native snakes within the Arklay Mountains that were infected by the outbreak caused by James Marcus. A significant number of Adders appeared within the courtyard area of the Arklay Research Facility, showing they favored moist regions. Their venom was greatly strengthened by the T-Virus, which can also be spread through said poison. This and the increased aggressiveness, however, were the only symptoms of the T-Virus the adders displayed. Compared to the Yawn, which was created through research carried out by Umbrella, the Adders are a minor threat at best.

Appears in: Resident Evil (Original PSX version, Deadly Silence, and GameCube remake), Resident Evil: The Umbrella Chronicles