It was so, so cold.
Karkaroff did not know how they managed to keep himself and the others alive in this cold. There were no fires or obvious Insulating Charms at hand; the cold penetrated every layer of his body, his fingernails were always blue, yet he did not become hypothermic. Not during the daytime, anyway.
Shivering, Karkaroff pressed his spine to the freezing stone wall, curling instinctively to conserve body heat. He tried to remember Warmth, and a vision flickered past – bright torches, crackling gently, lining the classroom's walls – but the image disappeared instantly.
It was so, so cold...