Zorgan and the Gorsemen: Book 12 by Georgie Adams
The world of Karisma is in turmoil: storms are raging and crops have failed. Queen Charm blames Zorgan for everything bad that has happened since he threw her charms away, so orders his capture by her soldiers. Zorgan gathers together his own army of Gorsemen - wild savages with hair as prickly as gorse bushes, who live on Heart Moor - bribing them with the promise of rich rewards, to defeat Charm's army. When Sesame arrives in this magical land, she finds herself walking into a raging battle. Once Morbrecia has witnessed Zorgan's explosive demise, Sesame must stop her becoming a powerful sorceress in his place, and find the next charm in a very prickly place.