Embrace of Shadows is a greater power acquired by vampires in The Elder Scrolls IV: Oblivion upon reaching stage four of vampirism. This skill can be used to bypass the huge disposition penalty that comes with being a high level vampire.
Being a greater power, embrace of shadows can only be used once per day.
It is commonly used to work around some restrictions gained when the Hero reaches stage four vampirism and becomes fear and hated by everyone. (with some exceptions, such as followers, the Dark Brotherhood, if the Hero is a member) because it makes it exceptionally easy to break into someone's house and feed on someone and revert to stage one.