Nicholas St. North and the battle of the Nightmare King - WILLIAM JOYCE

Forget the huge belly and the jolly old elf stuff because before Santa grew out the beard and shimmied his way down your chimney, he was a swashbuckling young man with a bit of a wild streak-and a talent for wizardry. When St. North's latest invention, The Robot Genie, falls under the spell of The Nightmare King, Santa pays a terrible price. He is shrunken, frozen in place and trapped in a metallic shell and turned into a toy which means he is powerless to stop The Robot Genie from enacting The Nightmare King's evil plot to terrorize children.
But, toys are magical things, aren't they? Without being able to speak or interact, they can form powerful and lasting bonds with young children, children who care for them and love them with all of their hearts-and when St. North the toy falls into the hands of a little girl who needs a toy more than most, they unlock the spell and set off a chain of events that send St. North on a sleigh ride through a starry, starry night…and lays the foundation for the next Guardian books.