Winter Masques is a sourcebook for Changeling: The Lost. It contains more options for player characters, in particular more information on the Seemings - including new Kiths and Contracts - and of Court structures beyond the seasonal courts common in the Western world.
From the Onyx Path catalog:
Fiction. Veles, a Moon Court spy, is captured by the Ogre Captain Doco and his Hounds of the Day.
An explanation of the book's goals (variety and multiculturalism), followed by a guide to the chapters that follow.
An in-depth treatment of the six changeling Seemings, including a new affinity Contract for each and discussions of the character traits and experiences that each may have.
More details of the Kiths presented in the core rulebook, as well as new Kiths for all six seemings.
This chapter addresses the nature of Changelings and their societies outside of the Western world. It includes additional Kiths to fill niches in the stories of different cultures and two examples of Court systems other than the seasonal Courts. There are also guidelines for creating characters based on folk tales from around the world.
"He never tried to tell you about his character."
-- Greg Stolze's description of Thomas Manning