The bheur, also called the "blue hag," is a powerful creature of legend, who dwells in the northern reaches, and arrives with the chill of winter. Legend says that there is only one bheur, and that when she arrives, winter comes with her, and spring only arrives when she is driven off.
The bheur is universally depicted as cruel and monstrous. She is a wrinkled old crone with blue-white skin and snow white hair, wielding a gnarled staff, and speaking with the howling of the winter winds. She preys on lone travelers, freezing them solid and then snapping off pieces of them to snack on. She is also said to be able to sneak into houses whose windows and doors are not sealed properly, snatching up children or sleeping residents.
The touch of the bheur deals cold damage, and are immune to such damage themselves. They are also cold enough to be protected against fire, taking less damage from it than from other attacks.
The blue hag is capable of using ice storm, wall of ice, and cone of cold.
The staff of the blue hag is a sacred object to her, enabling her to use her magical abilities. If it is lost or destroyed, the bheur must leave the world for one year to find a new one.
Those who witness a bheur eating a frozen creature become permenantly blind or insane.
Bheur are said to travel in the company of orglashes.
Marzanna, called "winter hags," are rapacious predators similar to the bheur, but significantly less powerful. They have the power to terrify (and kill from fright) with a gaze, and their rending claws are especially fierce. They have quite an array of magical abilities themed around stealth, cold, and curses, including control weather, nightmare, ice storm, wall of ice, numbing sphere, bestow curse, alter self, ray of frost, pass without trace, obscuring snow, ghost sound, and dancing lights.
Marzanna: 3e Frostburn