Picking up this relic will give the player a Necronomicurse, an unplayable Card that cannot be removed from your deck by any means and cannot be truly Exhausted. Attempting to Exhaust it will simply put it back to your hand.
This relic can be triggered on an X card, so long as it consumes 2 or more Energy. The second play will use the same value for X as the first.
This relic (especially its appearance) is a reference to the Necronomicon from Spelunky, which references the Evil Dead franchise, which in turn references the Necronomicon from the writings of H.P. Lovecraft, in which it is an evil tome containing otherworldly secrets that will drive humans to insanity merely from learning them.
Despite Necronomicon's description, Necronomicurse is scripted to have its existence tied with Necronomicon. Should Necronomicon be removed by any means (possibly via N'loth), Necronomicurse will be removed from the deck as well.