
If you're new to Resident Evil, that's probably the most important one to remember. By combining Progenitor with leech DNA, he was able to create the t-Virus, a series of mutated Progenitor strains which, when combined with Ebola RNA, is capable of turning those infected into zombies.

In 1978, a year after student virologists William Birkin and Albert Wesker joined the training facility, Dr. Marcus grew suspicious of Spencer’s intentions and attempts to steal his research, and wished to overthrow him as head of Umbrella. Tensions bloomed between Marcus and Spencer in the ‘70s and ‘80s. Marcus mostly used the position to focus on his Progenitor virus research. The point of the program was to train researchers for the highest ranks of Umbrella, but Dr. Marcus reluctantly took over as director. The same year Umbrella was founded, the company built the Umbrella Executive Training Center in the Arklay Mountains, which Dr. If you're playing Resident Evil 2 for the first time, Birkin and the G-virus will be important names to remember. Over the course of Umbrella’s research on Lisa Trevor, which spanned over a decade, Birkin would discover a mutant strain of Progenitor eventually dubbed the G-virus.

Upon completion of the mansion in 1967, George’s wife Jessica and daughter Lisa were abducted by Umbrella and subjected to tests for the Progenitor virus. During this period of time, Spencer contracted architect George Trevor to design and construct the Spencer Mansion, the gothic estate and secret Umbrella laboratory that our heroes eventually stumble upon in the Arklay Mountains.
