Alan Dean Foster 
Hour of the Gate [EPUB ebook] 

THE DREAD RETURNSJon Meriweather, plucked from his own world to a place where animals walk, talk and cast spells, is pitted once more against a deadly foe. Now he and his strange fellowship must embark on a journey from which none has survived.His way lies down the treacherous river that winds through the subterranean lair of Massaurath, Mother of Nightmares, across Helldrink through a tunnel of cold flame to the centre of the Earth…