In many cases, the victim of an undead vampire is attacked while sleeping. This phenomena often resembles attacks by such entities as the Anglo-Saxon mare, the Scandinavian mara, the Slavic mora, and sometimes even the incubus or succubus.

In the case of the Buckinghamshire vampire which occured in England in 1196 and was chronicled by William of Newburgh in his Historia Rerum Anglicarum, the revenant was sais to attack his widow while she was asleep. He awakened and alarmed her by leaping upon her and almost killing her with the full weight of his body. The same thing occurred every night. The widow then solved the problem by having relatives stay with her at night to help keep her awake.