The Ouroboros Key by Patricia Leslie

Prophetic dreams have haunted Dan Tenney since childhood, foretelling him of a life-changing event that is soon to take place. But before he can learn the meaning of his visions, he is attacked by a shadowy group of extremists: the Brotherhood of the Grail. Finding sanctuary underground, an ancient relic comes into his possession and Dan begins to understand the path his visions have laid out before him. His quest will be fraught with an otherwordly people and an event that could tip the balance in favour of human existence—or disastrously against it. The mysterious Brotherhood will do everything in their power to prevent Dan from fulfilling his destiny as the Bearer of Ouroboros.