The Shadow Dragons (Chronicles of the Imaginarium Geopraphica, Bk. 4)

The Caretakers of the Imaginarium Geographica are at war. The Imperial Cartological Society, led by Richard Burton, have collected all of the doors from the Keep of Time, and are building a new tower in our world at the request of an old enemy: The Winter King's Shadow. He has a terrible weapon - The Spear of Destiny - that can be used to command the shadows of anyone it touches...including the protectors of the Archipelago, the dragons. With a ship called The Iron Dragon, the Shadow King regains passage to the Archipelago where he uses the power of the Spear and the portals of Time to enlist an unstoppable army of Dragon Shadows. And after the Archipelago falls, he intends to betray the Allies in our world - but not to align himself with the opposition. The Shadow King intends to use the turmoil of WWII to take over BOTH worlds.

All the legendary Caretakers, past and present, come together on a great island in the northermost part of the Archipelago to decide the ultimate fate of the Imaginarium Geographica, as a terrible battle ravages the lands around them. And their only hope lies with a small group of companions who are on the quest for the broken sword Caliburn: the Grail Child Rose Dyson; her mechanical companion, the owl Archie; a mouse with an attitude; a dead Professor of Ancient Literature; and the mythical knight, Don Quixote.

They must sail beyond the ends of the Archipelago in search of the sword, and the only being alive who can repair it: a scholar, who, once upon a time, was called Madoc.