The Hebrew ovoth (אֹבוֹת) is plural of ov (H178) and refers primarily to ancestral spirits or familiar spirits invoked through necromancy. Secondarily the word can refer to leather water skins.
The Mosaic Law explicitly forbade consulting ovoth (Leviticus 19:31; 20:6). Saul's tragic end was precipitated by consulting a medium at Endor (1 Samuel 28). God alone is the source of wisdom and life — consulting the dead is a rejection of His Lordship and invites judgment.