Seed of the Nightmare Spell

The Seed of the Nightmare Spell is revealed to be located at the very top of the Tomb of Ariel, forming its capstone, and is described as fundamentally unlike any other Seed. While the structure of Tomb of Ariel is composed entirely of Seeds of Nightmare—ranging from lower Rank ones at the base to increasingly more harrowing ones higher up—this particular Seed is singular and that there are no Seeds in existence like this one. It is identified paradoxically as both "the last one" and "the first one", ultimately clarified to be the Seed of the Seventh Nightmare. This Seed is not merely another Nightmare, but the source of all other Seeds and the root of the Nightmare Spell itself.^[1]

The Seed of the Seventh Nightmare is equated with the Nightmare, specifically the Nightmare of the Forgotten God, whose consciousness is imprisoned within it. Its presence explained the otherwise unfathomable nature of the Tomb of Ariel—how a single structure could give rise to innumerable Nightmares—and may also relate to the existence of the Nightmare Butterflies inhabiting the pyramid, which are implied to feed on the emanations of these Nightmares. The Seed's power and nature are so overwhelming that even perceiving it poses extreme danger: gazing upon it is likened to looking directly into the Void, with the risk that one's soul could bloom with the vile, virulent darkness of the Corruption.^[1]