Ocyrhoe, a, cunning fugitive from Rome, safeguards a chalice of subtle but great power. Getting herself in France, she allies using the persecuted, pacifist Cathar sect within their legendary mountaintop stronghold, Montségur. There she resists providers from the Roman Cathedral and its own Inquisition, fights off escalating, bloody besiegement by troops of the Ruler of France, and shields the inexplicable cup from the designs of several. Percival, the heroic Shield-Brethren knight in the Mongoliad, consumed about Siege Perilous by his mystical visions from the Holy Grail, is certainly also drawn to Montségur – where the chalice holds the main element to his future. Arrayed against Percival and Ocyrhoe are enemies both old and brand-new who are established to reveal the secrets from the Shield-Brethren with the hope of destroying the order once and for all. Alive with unforgettable personas, intense with actions and intrigue, Siege Perilous conjures a middle ages world where the causes of faith confront the makes of fear. Choices made by personas in The Mongoliad reach their greatest conclusion in this 5th and concluding book – and all of Christendom is at stake.