Shadow Steed — Richard A. Knaak

The prosperous mountain kingdom Talak survived war with the Ice Dragon unwounded -- except for young, mutilated King Melicard's hatred of dragons, drakes, and magical humans like Cabe and Gwen Bedlam. Pursuing his twisted vendetta, Melicard captures the demon steed Darkhorse but unwittingly frees the sinister pan-dimensional entity Shade, a being who has found the ultimate spell of world-dominating power. At once Shade plans to test his deadly rites -- on Melicard's betrothed, the beautiful Princess Erini.

Now, to save his beloved and his world, the mad king must trust his foes, join with his enemies, and ride with Darkhorse on a lethal plunge into the depths of what he fears most... The heart of Dragon magic.