What are the "seven golden keys" in the novel, The Magician King?

The seven golden keys are seven golden magic keys crafted by the people who first accessed the magical system of the gods. While they keys have been used for various purposes throughout history (such as in the fairy tale “The Seven Golden Keys”), their original intent was to unlock the last (or back emergency) door to the world of magic should the gods ever decide to try to seal off magic from the rest of existence.