In the Babylonian magico-medical tradition, Šulak is the Lurker of the bathroom or the demon of the privy. Šulak appears in the Babylonian Diagnostic Handbook (Tablet XXVII), in which various diseases are described and attributed to the "hand" of a god, goddess, or spirit. A "Lurker" is a type of demon who lies in wait in places where a potential victim is likely to be alone. When a man attends to excretory functions or elimination, he is exposed and hence vulnerable: "Šulak will hit him!" The "hit" may be a type of "stroke" (mišittu). The demon referred to as "The Hitter" or "Striker" elsewhere in the handbook may be Šulak identified by an epithet. A much earlier reference to this demon is found in a Hittite diagnostic text.
The "demon of the privy" (Sheid beit ha-Kisset) appears also in the Babylonian Talmud: The Rabbis taught: On coming from a privy a man should not have sexual intercourse till he has waited long enough to walk half a mil,— because the demon of the privy is with him for that time; if he does, his children will be epileptic.Stroke and epilepsy were closely related in ancient medicine. This law is not included in the Mishneh Torah. The lavatory demon takes the form of a goat in the Talmud (Shabbat 67a, Berachot 62a).
The "demon of the privy" is the type of unclean spirit that in the early Christian era was regarded as causing both physical and spiritual affliction.