A patron deity is a sire of a race; for example, Glycon is the patron deity of the Glykin. They have blessed what were once Humans, changing them into an entirely new existence as a different race. Those who are 'adopted' by a God receive qualities that the god possesses, such as in the above example, where the Glykin received protective scales.
There is no historical evidence to back this up, however, and so many people (especially humans) understandably doubt whether or not this is true. Zerans firmly believe it, even to this day, and Glykin are more likely to believe than others. Many others believe it doesn't truly matter either way.
On some occasions, a patron deity may be worshipped by a member of a race they did not sire.