Albert Wesker is a virologist mastermind, who aims to infect the entire world with his virus, Uroboros.  Uroboros is a virus that appears as black, gooey tentacles, and will do one of two things to the host.  If they are compatible, it will give them superhuman powers, such as speed, strength, and intelligence.  If they are not compatible, Uroboros will take over their mind and turn them into a monster.  Albert Wesker wants to infect the entire world with Uroboros.