Storing Energy In Bells.

[magnum.arcanum]

The bell was to be wrapped in green taffeta and placed in the middle of a grave in a cemetery.  It was to be left for seven days, during which time it absorbed certain vibrations and emanations.  At the end of a week, the bell was properly “cured” for Necromancy rituals.

I take it, Iron or Silver was used for this.  The enemy apparently promoted this ritual which would in effect surround others with grey energy (bad).
Was that the point of these rituals.  What was the point?