Phasal Magic

To be gifted with phasal magic means to have a property that defines you changed as The Phasal Tree binds you to it. Everybody gifted so has had a property of their own permanently changed, and can alter certain Properties around them.
Their own changed property usually comes into play when they use their gift.
Phasal magic can bring people across world boundaries to Fairtree, although there are some who believe the phasal-shifted are instead created by the magic, complete with a backstory. This is not a common situation, but perhaps 4-6 new residents a year claim they came from another world. (One notable has demonstrated the ability to summon (and later banish) seven alternate versions of herself when she needs assistance.)

Manifestation

Most manifestations of phasal magic are best considered a 'quirk,' although there is no widely accepted definition of the term. Those so gifted can perform small magical feats, what a Far Fairlian might describe as a single 'spell': helping plants grow, changing the color of something, levitating, lighting small fires, and so on. Quirks rarely cause problems beyond the interpersonal.
Other manifestations are comparably powerful but only rarely invokable: the child who calls a mother for themselves across dimensions; the woman who unleashes devastating force only when her life is in danger; the boy who teleports home as soon as he realizes he's lost. These powers can change, save, and destroy lives, and some of the city's researchers and rulers try to keep tabs on those so gifted, for reasons of their own.
Occasionally, magic as flexible as Far Fairlian Magic, or as dangerous as Crux Magic, appears. These people are highly sought by the various factions of Fairtree, and if they survive the first few weeks, are generally not allowed peaceful, quiet lives (unless the faction they align with supports this).
Very, very rarely, there are those who develop a personal magic on the level of the Archmages. Those either become known as an Archmage themselves, or attempt to carve out their own territory in ways that generally require Archmage intervention and go down in infamy. There are also rumored to be those who simply want that quiet, peaceful life--and have the power to insist they get that.

Being Changed

Everybody with phasal magic has been marked some way by it. Some changes may be ongoing, permanent, and minor, such as an unnatural haircolor or altered eyes. Other changes only manifest when a power is used, such as things around them catching on fire, or odd hungers. They are very rarely harmful to the changed, although they may be harmful to their surroundings.