These sinful rites and these her sister’s songs Abhorred Erichtho, fiercest of the race, spurned for their piety, and yet viler art practised in novel form. To her no home beneath a sheltering roof her direful head thus to lay down were crime: deserted tombs her dwelling-place, from which, darling of hell, she dragged the dead. Nor life nor gods forbad but that she knew the secret homes of Styx and learned to hear the whispered voice of ghosts at dread mysterious meetings.– Lucan, The Pharsalia
The eponymous witch, Erichtho, eats corpses, sacrifices babies and forces the dead to speak. The ritual for the latter, in particular, is quite a nasty scene, well worth reading if you’re a fan of cosmic horror.
Interestingly, Thessaly was infamous as a haunt of witches, and such stories have persisted since the Roman period. The Thessalian witches were known for their ability to ‘draw down the moon’, an ability as evocative as it is ill-defined.