Regular and repeated application of Avacynian magic can help prevent the change to canid form. Roadside shrines, prayer, angelic rites, the blessing of accomplished clerics, and the presence of holy symbols all help reinforce the werewolf's humanity, helping her hold on to her human form.

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The full moon, however can overcome even powerful religious precautions. In addition, the power of angelic magic has waned in recent times, and werewolf transformations have become more common and harder to predict.

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PLANESWALKER'S GUIDE TO INNISTRAD: KESSIG AND WEREWOLVES