Necronomicon is a Relic obtained through the Cursed Tome Event.
Picking up this relic will give the player a "Necronomicurse", an unplayable Card that cannot be removed from your deck by any means.
The Necronomicurse counts for Du-Vu Doll.
Interestingly, the Omamori will in fact negate the Necronomicurse entirely.
Trivia 
Edit
- This relic references the Necronomicon from the writings of H.P. Lovecraft, an evil tome containing otherworldly secrets that will literally drive humans to insanity merely from learning them. The appearance of the icon is specifically drawn from the depiction of the Necronomicon from the Evil Dead horror-comedy movie franchise.
