A Godfest (GF) is an egg machine that arrives twice a month (typically in the middle and at the end of the month) in which Godfest Exclusive (GFE) cards become available for two or more days. As of 2019, almost every Godfest has been a Super Godfest, which has higher rates for GFEs but cost 
10 Magic Stones per roll (as compared to a regular Godfest).
Keep in mind that not all GFEs are available in every Godfest, so check the lineup in-game to see what is featured!