A Crystalized Crown in the shape of a Tiara, as it was covered in freezing cold frost, and neon glowing blue and white diamonds that light up, and it's made from ice and snow, fit for Princess Winter, Princess of the winter. 
Once someone or something puts it on their head, they will turn into Princess Winter, they will no longer be themselves, but only Princess Winter, but even after taking it off, they'll remain in the Princess Winter form forever and ever permanently. 