Umbrella began using their newly-developed t-Virus strains on animals soon after their founding. However, they were met with problems with their practicality, such as a lack of intelligence or insufficient strength increases which eliminated the Web Spinner as a reliable weapon. In its place, the Chimera project was started, which intended to insert insect DNA into human zygotes, then artificially inseminate the modified zygotes into the bodies of homeless women kidnapped by Umbrella to carry them to turn. A fly-human hybrid was their choice for the prototype, and was subsequently cloned.[excerpt 1]
Due to their many flaws, further research into more advanced forms was never conducted, and the Chimera's basic form was never refined to the lengths of the Hunter or the Tyrant.
Several Chimeras were encountered by the S.T.A.R.S. members during the Mansion Incident. In addition, Albert Wesker, shortly after regaining consciousness after the Tyrant "killed" him, encountered a Chimera while attempting to escape, only to effortlessly kill it with a single kick due to his newfound superhuman abilities.
Still, Umbrella continued at least a limited production of Chimeras in other facilities for a number of years, as several were discovered during Chris and Jill's raid on their Caucasus Laboratory, as well as during Wesker's own raid on the facility.