(Capcom's primary storyline)
"This is the t-Abyss virus, and we are equipped to infect one fifth of the earth's waters."
The t-Abyss virus would be developed by a team of scientists at Montpellier University of Marine Science conducting deep-sea investigation at the Kermadec Trench with an unmanned exploration vessel. On their fourth expedition, reaching the Hadopelagic Zone, the scientists discovered a new virus in the body of a deep-sea fish, a virus that allowed the fish to survive in such great depth - they dubbed it the Abyss virus, after the fear of unfathomed depth. The t-Abyss virus was created by combining the Abyss virus with samples of the t-Virus.
The creation of the t-Abyss virus demonstrated the ease of developing viruses that can mutate across species - mammals were just as susceptible to its effects as the fish that originally carried the Abyss virus. Although there were only a few incidents where the t-Abyss was used to attack, new types of B.O.W. were quickly developed with every use of the new pathogen.
After the events of Revelations, former FBC agent Raymond Vester visits his partner Jessica Sherawat in a cafe. He gives Jessica a vial of t-Abyss virus sample for her to bring to her employer, the TRICELL corporation. It is unknown what happened to the sample afterwards.
These are the list of known mutations that were brought about by the t-Abyss virus:
Because of the virus' corrosive nature, any organism infected by the t-Abyss will experience varying mutations, such as heavy physical deformity or losing body parts like lower jaw or fingers. Those infected by a stronger strain of t-Abyss will suffer horrific mutations to the point of being unrecognizable from their former self. The t-Abyss virus displays the ability to mutate any given organism, including those which were exposed to other viral agent.
Certain humans have genetic resistance to the virus. However, this does not guarantee immunity to the virus as they too mutated into B.O.W.s, notably the buzz-saw-handed Scagdead.