Blood Trillium by Julian May
It is now twelve years since the events recounted in Black Trillium. Haramis has devoted herself to the study of magic and science; Anigel and her loyal husband, King Atar, givern their provinces with affection, seeking always to teach and see the bright side of life; Kadiya has not changed - she's still impetuous, wild... and careless. There are problems but the world seems peaceful enough.
Then it all changes. Kadiya loses her talisman in the deep waters off the Windlorn Isles and Anigel's husband and children are kidnapped by a mysterious sorcerer who goes by the name of Portolanus. The ransom for their return? Anigel's talisman.
The world is losing balanc. Storms rage, wars loom. And Portolanus is smiling...