The All Seeing Eyes of God is an artifact given to Leonardo Watch by Riga El Menuhyut in exchange for his sister's sight prior to the beginning of the series. They are considered to be a divine miracle and as a result are incredibly valuable.
History
Prior to Leonardo Watch, there have been at least 53 other confirmed records of the All Seeing Eyes of the God holders in both the human world and the alterworld. In all instances of people receiving the eyes, the person closest to them has their own vision taken away. Riga El Menuhyut only appears to give the All Seeing Eyes of God to humans when a major cataclysm occurs in the human world, such as the advent of Hellsalem's Lot, in order to record them.
Description
The holders are chosen as the observers of major world-changing events, willingly or otherwise, and a contract is made between the holder and Riga El Menuhyut. In exchange for the eyes, the person closest to the holder is blinded. This serves as both a sacrifice for the manifestation of a divine miracle and as an anchor to keep the holder of the eyes in check, so that they cannot act rashly and can only observe obediently in the stead of the celestial beings.
As it is the result of a contract with a celestial being, the All Seeing Eyes of God cannot be surgically removed nor can they be cured or returned to what they were before. Doing so would be the equivalent of forfeiting the contract made, and a price would have to be paid for such an act.
Powers
Holders of the All Seeing Eyes of God are able to see the 'The Truth' of the world. Possession of the Eyes gives their wielders numerous abilities including heightened visual senses, allowing them to see fast movements normally impossible for human eyes to follow, or minute details with great clarity. They are also able to see past world altering illusions and perceive an individual's unique aura, including the scarlet feathered aura of a Blood Breed. Observing an Elder Blood Breed for a set duration can also reveal their "true name" if its heart is present.
Eye holders are also capable of altering and controlling the vision of those around them, such as switching two people's field of vision, inducing nauseating hallucinations, projecting what the holder sees into the minds of others, and the power over visual illusions in general. The eyes also allow the holder to see through another individual's eyes and observe past events that they have witnessed.
Using the eyes however has its limits, as they overheat upon prolonged use of their abilities. If the eyes sustain enough damage that they crack, the cracked eye's powers cannot be used until they heal. Physically damaging the eye beyond repair will cause the eye to explode, killing the holder.