Witching Night

Almost everyone in the Empire looks to the night before the New Year, known as Witching Night (or, in older times, called Hexensnacht), with particular dread. This night is sacred to Morr, whose priests are the only ones brave enough to leave the safety of their homes in order to conduct their rites in the graveyards. The line between the worlds of the living and the dead is particularly blurred on this night, and the spirits of those who have gone before sometimes come back. The vile Undead are seemingly energised by the wan, pale light of the moons on Witching Night, and shamble through the countryside, terrorising the living. Because the regions of death and sleep are so close, vivid dreams on this night give clues of a person’s fate for the coming year.1a

Source
Warhammer Fantasy RPG 2nd ED -- Tome of Salvation -- pg. 144