A long time ago, the Vile Thieving Bird stole one of Weaver's eyes… and to replace it, Weaver wove a new enchantment into their fearsome mask.
[Where is my eye?]
When the enchantment was activated, the great tapestry of fate revealed itself to the person wearing the mask — either the original one or one of the two Memories of it Weaver had bestowed upon the High Priests of the Nightmare Spell.
The original mask was long gone, having perished with the Demon of Fate. But at least one of the Memory pair remained, and had been found by Sunny in the stone cell under the ruined cathedral of the Dark City… which meant that he could glimpse the vast infinity of fate, as well.
The problem was that mortals were not meant to behold it. The oracles of the nameless realm from which the Nine hailed from lost their sight as a result of catching a glimpse of the great tapestry... but really, they got off easy.