The Diminishing Spell was a spell that can diminish the target, weakening and injuring them inside out. It is even able to greatly annoy an entity like the Darkness, although not to the point of causing any serious effect to it.
The spell itself came from the Book of the Damned.
The supporting team must prepare a caldrun atop an intricated sigil (very similar to a voodoo veve). A target's voodoo doll must be placed inside of caldrun and ignited. As one of the members plays the drums, all the members must recite a Latin word:
- Attenuare (means "Diminish" or "Weaken")
After the mixture ignited, the relay witch could relay the spell stronger thanks to union of multiple casters and cast powerful purple lightning to strike the target. The spell was powerful enough to weaken The Darkness somewhat and leave her with burns on her face and shoulder.
If the target is strong enough, the target is capable of backfiring the spell to the relay witch. Although the relay witch won't be killed by the backfire, the spell will relay back to the support team, killing them by burning them from the inside out.
In the Season 13 episode Funeralia, a full-powered Rowena casts this spell on Billie, but this time on her own and without reciting the incantation. Billie, now with the powers and cosmic position of Death, was left completely unfazed. Moreover, the amount of power Rowena used in the spell exhausted her powers to the point that she didn't know if she would ever recover all of the power she used.
- Although it came from the Book of the Damned, the spell itself is in Latin rather than Sumerian.