The Chessmen of Doom — John Bellairs

Why a dead eye in a room with no view?
Why pallid dwarves on a board that's not true?
To pull the hairy stars from their nest
And give sinful humans a well-deserved test.
If you solve this riddle you may wish you hadn't.
Peregrine P. Childermass

Upon Peregrine's death, his brother Professor Roderick Childermass receives this very strange riddle along with the terms of Peregrine's will: The professor must spend the summer on Peregrine's estate or forfeit his huge inheritance, And Peregrine, who dabbled in sorcery, left no doubt that danger lay ahead. But the professor and his young friends Johnny and Fergie, ignoring the risk, journey to the desolate mansion. There they battle a madman who is determined to let nothing -- and no one -- stop him from destroying the world.