Icon of St Largoth
The Eyes have been stolen and taken to Devil's Tomb deep in Graven-Tosk. Looking through them reveals all invisible and hidden things — including the otherwise-hidden passage to the Plant of Life. The Eyes are kept in the Drowned Hoard within the tomb.
The recovery of the Eyes is the hook for the Devil's Tomb scenario: "The Eyes of the Icon of St Largoth have been stolen and taken to a formerly abandoned hellhole deep in Graven-Tosk known as Devil's Tomb. They will see that which is hidden. Retrieve them!"
Devil's Tomb, Graven-Tosk, Plant of Life, Drowned (current custodians)
Who or what St Largoth was — and where the rest of the icon currently rests — is unwritten. The patron who originally hires the PCs to retrieve the Eyes is left to the GM.