DEVIL was a vaccine created to prevent Golgotha infection. It was developed by a top-secret team of Umbrella USA virologists led by Dr. William Birkin at the NEST. The name was a play on Dr. Birkin's wish for Golgotha to turn humans into god-like beings.
One critical aspect in "G" behaviour is their reproductive instincts, which take the form of parasitising humans with embryos. If the embryo and host are a close genetic match, the embryo implant onto the host and infect the body with Golgotha, turning them into another "G". As this process can be slow, it is possible to vaccinate a patient shortly after parasitisation. The only known occurrence was of Sherry Birkin, who was vaccinated a few hours after parasitisation by her father. Though it was too late to prevent any mutation, the virus' only effects were radically improving her ability to heal.