Letty Whiterock

Letty is a seasonal youkai who's only seen during winter. She seems fittingly cold towards most of the humans she meets, and is feared by humans as she is known to freeze them. She possesses an ability to manipulate chilliness. Since this is equivalent to an ability that manipulates the winter within nature, she possesses tremendous power according to the environment, but she is pretty much powerless outside of winter. Letty herself said that outside of winter, she hides away in a place where not a ray of sunlight can reach. During winter she spreads snow over Gensokyo. (Source: Touhou Wikia)