Dr. Louis "Lou" Hastings was a disciple of Hell who ensured the birth of the new Antichrist.
When Delia is eight years old and is injured falling off a horse, Dr. Hastings, while examining Delia for Gene and Karen York, removes the embryo of Delia's vanishing twin from her. Some days - weeks later, when Karen is hospitalized after witnessing Jo Thueson's death, Hastings implants the embryo of Delia's vanishing twin into Karen; for Karen to act as a surrogate mother for Delia's twin, who will become the new Antichrist.
Nine months later, Dr. Hastings helps Karen deliver the new Antichrist, Alexander. Some days - weeks later, Karen goes to Hastings and interrogates him; impaling his hand with a scalpel.
After admitting to Karen about Delia and Alexander's true identities, as well as the plot to use Gene's political status to ensure Alexander's rise to power, Hastings tries to shoot Karen; prompting her to kill him by stabbing him with the scalpel.
Hastings appeared to be old friends with Gene.
Hastings was sarcastic and friendly towards Delia while examining her.
Hastings normally acted kind, helpful and friendly towards Karen, but after the latter discovered Delia and Alexander's unholy identities, Hastings tried to kill her.