"Beware the unanswered riddle."
I just finished The Riddle-Master of Hed, book #1 of Patricia A. McKillip's Riddle-Master Trilogy.
Never let your enemies build walls around you, least of all walls of ignorance propped up by truths and knowledge. Thus is the first part of the riddle of Ghisteslwchlohm, and the fate of the Wizards' City of Lungold, solved, a tad late, by Morgon the Star-Bearer as a war long silenced begins anew. A war that is the ultimate Riddle Game.
"Beware another riddle-master."