The Sapphire Portal. The Gates of Good & Evil, #4

The world of Santhenar has fallenMost of the old allies are dead or captured, and the conquering Merdrun are carving Skyrock into a gigantic tower, with a sapphire-clad tunnel at its base. Is it a horrific new weapon to cleanse the world, so they can take it for their own? Only their arch-sorcerer, the sickening, life-drinking magiz, Dagog, knows. Karan, Flydd and their broken allies have only thirty days to find the answer.
Thirty days to unlock nine-year-old Sulien's hidden memory and reveal the Merdrun's one fatal weakness. But Sulien has been abducted by the magiz, who needs her talent of far-seeing for his monstrous conspiracy. To save her daughter's life, Karan will have to break into a compound guarded by 150, 000 enemy troops and every magical device known to the enemy. Assuming she can get past the traitor in the allies' ranks.
You won't want to miss this truly epic fantasy series by a million-selling authorWhat reviewers say about the Three Worlds books"A compelling adventure in a landscape full of wonders." - Locus"A page-turner of the highest order . Formidable!" - SFX on Geomancer"It is the most engrossing book I've read in years." - Van Ikin, Sydney Morning Herald"Readers of Eddings, Goodkind and Jordan will lap this one up." - Starlog"Utterly absorbing." Stephen Davenport, Independent Weekly"For sheer excitement, there's just no one like Irvine." SFX on The Destiny of the Dead"As good as anything I have read in the fantasy genre." - Adelaide Advertiser