Melinoe will mention the idea of the wards to Hecate when she meets her after speaking with Hermes, and after another night or two, you should have the Permeation of Witching Wards incantation ...

Having turned away from Lucifer, Zelda's coven needed a new source of power, and there was no better choice than the goddess of witchcraft herself: Hecate. So, just who is Hecate in Chilling ...