Clairvoyance

Some fey and humans are born with the ability of clairvoyance. Even though the fey are magical beings, the chances of a clairvoyant being born among them are about the same as the humans.The exact abilities vary from person to person, but they generally manifest as foresight, and the ability to see through illusions.
Most of these abilities are unique to the clairvoyant, and only a few, rare items, such as the Sleeping Eye Knife, can actually achieve similar feats.

Manifestation

Most people with clairvoyance have subtle marks on their forehead. These marks typically take the shape of an eye. Sometimes they take the shape of a celestial body such as the moon or the stars. In the most extreme cases people are born with a physical third eye.
Clairvoyance typically appears at birth, and very rarely does it manifest later in life. Clairvoyance is not hereditary, and it is very difficult to predict whom it will manifest within. However, it is significantly more likely to manifest in people who are blind of who have visual impairments.

True Vision

Almost all clairvoyants with working eyesight have this ability. It is relatively simple in that it allows them to see if something is an illusion. It also allows people to see that which is invisible.

Foresight

Clairvoyance, like all forms of magic, relies on the power of dreams. It is believed that people recieve visions from the Dreamscape of possible futures, but visions are not infallible and do not always come true.

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There is a theory that foresight does simply allow the person to see a possible future, but that it shapes the future and warps reality to fit the vision of the clairvoyant.

Dreamscape Visions

Different from foresight, these visions allow clairvoyants to see beyond the realm of Reverie and into the dreamscape. Many of these visions can drive people mad, but it is one of the most powerful abilities available to the clairvoyant, allowing them to access powerful and otherworldly magic. However, it is also one of the rarest. Generally there is only one person alive within Reverie who has this ability at any given time.

Prompt - Are some people in your world born with a "third eye" or another kind of non-physical sight? What do they see?