Albishadewe: Quest for the Unicorn — Laraine Anne Barker

In the centre of the bier lay Ignarius in a simple white robe. … A silver coronet was his only adornment. No king could have looked more regal or dignified. … It was hard to believe so much evil existed within him.
“Touch him!” Mirabell hissed into Esmé's ear. … The contact sent shudders of revulsion right through her. … She found it impossible to believe living flesh could be so cold.
Mirabell whispered again: “We're going to drain the warmth from your body to warm him -- transfer the beat of your heart to his -- drive the breath from your lungs to make him breathe again.”
Esmé felt her heart lurch in shock. Did Mirabell mean what she thought? She turned to look at the sorceress -- and the glint of relish in Mirabell's eyes told her the answer. Horror flooded through her. Its frigid touch seemed to turn her blood to ice.

Mirabell has captured the white unicorn and all thirteen dragons and also stolen the Godking's treasure. Now she has abducted the Princess of Lazaronia. For it seems that only the life in Esmé's body can bring the wizard out of his eternal sleep. But the sorceress's evil experiment means certain death for the Princess …