Brooks Terry. Magic Kingdom for Sale. Sold!

Del Rey Books, 1986Annotation: Landover was a genuine magic kingdom, with fairy folk and wizardry, just as the advertisement had promised. But after he purchased it, Ben Holiday learned that there were a few details the add had failed to mention.
The kingdom was in ruin. The Barons refused to recognise a king, and the peasants were without hope. A dragon was laying waste countryside, while an evil witch plotted to destroy everything.
To put the final touch on the whole affair, Ben soon learned that the Iron Mark, terrible lord of the demons, had challenged all prospective Kings of Landover to a duel to the death – a duel which no human could hope to win.
The task of proving his right to be King seemed hopeless. But Ben Holiday was stubborn…Questor Thews
Sterling Silver
Coronation
Paladin
Lords of the Greensward
Willow
River Master
Elderew
Crag Trolls
Crystal
Deep Fell
Fairy
Io Dust
Strabo
Abaddon
Iron Mark
Medallion