Nosferatu is the name given to a hideous, near-indestructible irregular mutant born from the T-Veronica virus in Resident Evil CODE: Veronica. This abomination was once human, but was transformed into a monster as part of an experiment to see the results of injecting a living human with the T-Veronica strain.
The creature known as 'Nosferatu' was once known as Alexander Ashford, the sixth head of the noble Ashford family. Alexander was a high-ranking official within Umbrella and his own father Edward Ashford was one of the corporation's three founding members. Edward had died shortly after the founding of Umbrella and Alexander was forced to take his place as head of the Ashford legacy before he was ready. Under Alexander's leadership, the Ashfords lost a great deal of their power and influence and Alexander was seen as a disgrace to the family line.
Alexander attempted to restore the Ashfords' credibility by dedicating himself to his research in genetics, particularly in the study of the human genes that regulate intelligence. He knew he could never restore his family's honour himself, so he intended to create a perfect heir that could accomplish what he couldn't. Using his own DNA and the DNA of the Ashford family's matriarch Veronica that he stole from her grave, Alexander devised an advanced cloning method that led to the creation of his twin 'children': Alfred and Alexia. Alfred was of above normal intellect, but not a genius, whilst Alexia possessed unmatched intelligence, and went on to become a Chief Senior Researcher at Umbrella at the mere age of ten. The creation of these twins was horrifying at best. Finding it unbearable that anyone should find his records, Alexander hid them in a secret room at the Antarctic Base.
However, over a decade later, Alfred found the secret room, but was unable to open the doorway, requiring three family gemstones to open it. He easily accessed two of them, as they belonged to him and his sister, but tricking his father into surrendering his was another matter. He eventually succeeded, and opened the door. He read the records and went mad from the revelation that he was merely the unintended by-product of his father's experiment, and to the atrocious truth behind the experiments that ultimately resulted in his and his sister's creation.
Around this time, Alexander started to express concerns surrounding Alexia's obsession with the T-Veronica virus, a viral strain she had developed by combining the Progenitor virus with the DNA of a queen ant, and, in particular, her twin desires to experiment upon her own body with it and to release it into the world. His worries increased to the point that he installed an experimental anti-B.O.W. weapon known as the "Linear Launcher" in the facility as a last resort to stop her if she carried through on her plans.
After his children discovered the truth about their origins, Alexander found himself becoming Alexia's prisoner and test subject to test the effects of the T-Veronica virus. Injected with the virus directly, he was left locked away in a dungeon for two months as he mutated into a terrifying creature. The virus caused his skin to harden and large, tentacle-like appendages to grow out of his back; his muscle tissue expanded to the point where his heart broke through his ribcage and became visible. Disappointed with the results of her experiment, Alexia left him bound and caged in a hidden cell within the Antarctic Base. During his years of confinement, Alexander's inhuman screams echoed throughout the facility, disturbing all of the workers who heard his cries. Kept away from prying eyes, Alexander became known as "Nosferatu" among the base's staff.
Alexander would remain sealed away in solitary confinement for over fifteen years, but he would break loose following the T-virus outbreak at the Antarctic Base. Claire Redfield and Steve Burnside had attempted to escape from the base using a digging machine, but the damage caused by the digger allowed the Nosferatu to escape from its cage. It wandered out into the harsh Antarctic snow and made its way to a heliport where Claire and Steve hoped to access a chopper so they could escape the base. The creature knocked Steve clear of the platform and Claire fought against it using the sniper rifle she had taken from Alfred. Nosferatu's exposed heart made it vulnerable to precise shots and Claire was able to put an end to Alexander's living hell.
The Nosferatu still appears to be human on some level, but its skin has turned a deathly grey, its chest is torn open to reveal its beating heart and it has three long, multi-jointed limbs growing out of its back, each ending in a scythe-like claw. Its arms and legs are bound in a garment similar to a straitjacket and impede his movement to a degree, but the tentacles on its back compensate for this. It also wears a blindfold and so it cannot see, relying on sound and smell to track prey.
Nosferatu's tentacles are surprisingly strong, capable of letting the monster move around both on the ground and up walls; it can even swing from high vantage points and the limbs can pick up heavy objects. The creature's most notable ability is a strange toxic mist that it exhumes from its tentacles which can leave victims poisoned. Its mutated muscle tissue is strong enough to resist any impacts, but its exposed heart serves as a major weak spot.