Another bit of lore:

How to make a god:
1) Follow the "how to make an otherkin" steps with no regard for if the creature can reproduce with anything outside of its group.
2) Continue it for so long that the species you created is as far beyond humans as humans are beyond chimpanzees.
3) Congratulations, you made a god.

How to make a demigod:
1) Find a species you, as a god, want to interbreed with.
2a) Make sure it's within the first few days of pregnancy or
2b) Artificially impregnate it.
3a) Standard reproductive practices or
3b) Bodily fluid transfer of another type.
4) The Reproductive Retrovirus in your body rewrites much of the DNA in the cell/mass of a few cells.
5) Congratulations, you made a demigod.