Piers Nivans is a member of the North American Branch of the BSAA in Resident Evil 6.
He is a talented marksman, who served under Chris Redfield during the Edonian Civil War in 2012. On one of their missions, Carla Radames infects their comrades with the C-Virus and turns them into mutants. Chris is knocked unconscious in the ensuing battle but is rescued by Piers. Chris becomes disillusioned and disappears after recovering.
Piers tracks down Chris and successfully convinces him to rejoin the BSAA to avenge his dead comrades. They are deployed to Lanshiang, China and tasked to stop a bio-terrorism attack. The duo are eventually led to an underwater laboratory that is being used to create powerful bio-organic weapons. Piers is severely injured during their final battle with the B.O.W., Haos, and injects himself with the C-virus to continue fighting.
After he and Chris manage to defeat the Haos, they then attempt to escape the laboratory during its self-destruction sequence, but after realizing that he is beginning to succumb to the C-virus, Piers seals Chris inside an escape pod in order to ensure his survival, while he stays behind during the laboratory's destruction to prevent himself from mutating any further, sacrificing himself in the process. Right before his death, Piers manages to save Chris from the still-alive Haos by killing it as it attempts to destroy the escape pod Chris is in.
Chris honors Piers's memory by remaining with the BSAA (when before, Chris thought of retiring and leaving Piers in charge). Piers is mentioned by name during the epilogue in Resident Evil: Revelations 2, as he is in China with Chris.