So I haven't thought names for my characters so will call my protagonist Bob. In the 1800s, Bob works at a lab and him and his team was contacted about an alien that was killed. They bring it back to the lab and dissect it. Later that day Bob has a dream of meeting the brother of the alien called C. C tells Bob it will put its seed in a woman so she can birth a child that will bring a new age to man. Bob doesn't believe this at first but then C makes him see into the future. Bob sees he will become a pope like figure of the city and had started a new religion worshiping C. he goes back to work the next day to tell his coworkers that he has heard god talk to him. What my problem is how could he convince his coworkers of the being is god?
It seems pretty likely that he wouldn't be able to. If your story hinges on this, maybe C could give Bob some kind of ability to influence the others, whether directly or by showing them visions as well?
How important is that C sees Bob in the dream? Could it be it presents itself infront of his colleagues? Because even in the 1800's it's difficult to pull something this big of because someone had a dream. You will need some kind of physical proof or ability like izzybot mentioned.
Why would you want to make it easy for Bob? Not being able to convince his coworkers is a handy hill for Bob to climb, the process creates an arc, and all you need to do is define the stakes; what happens should he fail to prepare everyone for the coming of C? From what you've explained so far, you have some fixings for a good Steampunk version of the story of John the Baptist.
Hybrids for the sake of deus ex machina are not my forte. You have to explain to the reader how this prophetic stuff works. Sure he will get a following (and kinda gain a cult status), due to the fact that he will sound insane to the average person. And could lose his standing in the scientific community, as a result of such unproven claims. The biggest problem you face is the HOW? Dead things do not deliver messages to others, the dying can. Let alone how can they ensure that this new hybrid producing C will be able to genetically bear an alien/human hybrid? The odds are so small, that they are almost nil. It would take billions if not trillions of tries to even produce an offspring of cross species, and if successful would leave the offspring sterile. It all depends on how the science works in your world, and how plausible you want it to be.
