The Caul

Away from cities and their sages, many parts of the rural world hold a special fascination with birth cauls. In the western reaches of the Three Continents, children born with cauls are earmarked for training as seers or shamans, as they came into the world with part of the Veil upon them. In the middle regions of the Great Continent, a child born with a caul is viewed as mildly cursed, and special burial procedures are observed to ensure that the person doesn't return as undead. Among the Navigators, those born with a caul who later manifest a Mark (an extremely rare set of circumstances) are initiated into void navigation.
More cosmopolitan people tend to ignore cauls but some superstitions run deep, and an extra prayer or sacrifice to the gods is usually called for. Parents often don't even tell their child, as admissions of superstition typically make one stand out.
The truth behind these rumors is that they're often self-prophesying. A child groomed for trance magics from a young age will no doubt perform well at it, as well as most initiated so early. To be seen as a not-quite pariah by one's peers can lead to a lot of resentment that nurtures the conditions for returning as undead barring any exceptional burial, and as for the Navigators, void navigation is difficult but anyone with a Mark could theoretically do it, though the caul-born have a tremendous advantage in terms of time. The truth is that there really is nothing special about people who are born with a caul versus those who are not, though the expectations of everyone around the person so born can shape and mold them as surely as any other social conditioning. For those born in cities at least, there seem to be no consequences for it.