Malarkoi

Nathan Treeves is dead, murdered by the Master of Mordew, his remains used to create the powerful occult weapon known as the Tinderbox. His companions are scattered, making for Malarkoi, the city of the Mistress, the Master's enemy. They are hoping to find welcome there, or at least safety. They find neither - and instead become embroiled in a life and death struggle against assassins, demi-gods, and the cunning plans of the Mistress. Only Sirius, Nathan's faithful magical dog, has not forgotten the boy, and, bent on revenge, he returns to the shattered remains of Mordew, newly deformed into an impossible mountain, swarming with monsters. He senses something in the Manse at its pinnacle - the Master is there, grieving the loss of his manservant, Bellows - and in the ruins of the slums he finds a power capable of destroying his foe, if only he has the strength to use it.