The sapphire throne - Freda Warrington

In the second volume of her stunning Jewelfire Trilogy, Freda Warrington moves the action into a different plane of being - the world of the Aelyr, elf-like beings who claim relationship with Warrington's heroine, Tanthe.
The war seems to be over. Helananthe, granddaughter of the mad king, Garnelys, has gathered her forces and defeated the Amber Citadel of Parione and its evil Bhahdradomen advisers - but matters are not so simple.
The destinies of Tanthe and Ysomir, the sisters whose journeys from their village home of Riverwynde impinged so much upon the shaping of the war, have driven them apart. Ysomir is held in the palace, accused of killing Garnelys; Tanthe is pulled through a portal to the world of the mysterious Aelyr by a youth who calls himself her brother - an Aelyr youth. However, there are darker schemes afoot.
As the tale unfolds Tanthe faces challenges from her human friends and her Aelyr "family". Rufryd, brother of Ysomir's dead beloved, rages against the world, and becomes Helananthe's ambassador to the Bhahdradomen on the island of Vexor, where a terrible fate awaits him. And the Nine Kingdoms will be changed forever...