Aspect

Don't mind the teeth. Carl won't bite.

Aspects are magical parts of a mage's essence, a sort of metaphysical friction between the mundane reality and the glory within them. It leaks out through their flesh and out into the world, scarring both in the process. They can be either subtle or overt, and most fall somewhere inbetween - signs of someone of power for those who know what to look for, and someone strange to those who don't. For a mage, such obvious signs of being different can be more than a little inconvenient, sometimes even deadly. Others wear their Aspects like a warrior might battle-scars, as proud displays of who they really, truly are.

Mark of the Witch

Aspects are at their core manifestations of magic, changing the wizard's flesh or the world around him as reality buckles against the pressure of otherworldly power. Such manifestations are usually small and subtle, but some witches and warlock of particular might or misfortune become loci of unreality, with their very presence warping the world around them. Some changes are spectral, disappearing when touched, but others are very real.

In the right light, the Witche's eyes become like a cat's. In the moon, they glow faintly.

by Unsplash (Jaroslav Devia)

They are different from hexes, boons, or other lingering magical effects in that they are inherent to the core of a Mage's being, often part of their True Name. Aspects are part of who they are, for good or ill. Enemies who study a mage's Aspect can somtimes learn something to turn against them, but most are faint enough to not provide much.
Spirits, demons, and other creatures of the Beyond are able to read more from an aspect and draw almost prophetic conclusions from even small details about a wizard's personality or being. In turn, these creatures can turn helpful or hostile to certain Aspects, based on whatever inhuman logic governs them.

Carl, our wizard from the first quote, has teeth like a shark whenever he's in the dark.

Many Aspects are tied to mystic conditions, showing themselves when the stars - or something else - is right. The light of the moon, the turning tide, as anger rises or spirits fall, and a hundred other triggers can make an Aspect manifest themselves. Most mages have at least one Aspect, and many accumulate more as they develop their Art and grow into their magic. Like scars sometimes do, they mark progress.

Aspected Art

Some Aspects change not the mage, but their magic. It colors their spells with a subtle - or obvious - fashion, wreathing everything they do in flame and heat or charged with a hard, kinetic edge. It can be either helpful or a hinderence, but most learn to incorporate it into their Art and draw power from it. After all, their Aspects are already part of their being. These Aspects are less common and typically manifest in witches and warlock with greater magical ability or who've survived something real terrible.

Acquiring Aspects

Rain falls. My flesh sloughs off my bones. When I'm back in my body, something's different than when I left it.

Mages acquire Aspects as part of their journey. As they grow in might, learn new Arts, and become greater or lesser, they change and with that change come Aspects. Try as they might, no Mage has managed to figure exactly what kind of mechanic lies behind the manifestation of new Aspects, and they can develop at some cosmic whim.

Most Aspects come naturally, usually when the Mage has had some revelation and change in their lives, either mystical or mundane. As they become more comfortable and true to themselves or change as people, Aspects sometimes follow.

Emma's shadow moves on its own accord if she doesn't remind it to stay put. Sometimes, it steals things she secretly desires.

Others develop them in response to great ordeals or trauma. Surviving the Faelands, wandering the Beyond, or learning Things Man Was Not Meant To Know sometimes come with a change in perspective on life and with the change come the occasional Aspect.

by Rawpixel.com (Freepik)

The universe, and life, can be accused of having a sense of humor with these things.

by http://www.tribalartasia.com/

The Veil

Like a force of gravity that draws secrets to it, the Veil cloaks the truth from the uninitiated by changing memories, records, even recordings. The veil is why magic and monsters remain in the shadows, far from the public eye and out of the history books. Like a disease, it spread from one person to the next, changing what they were sure they remembered into something else.
Not even the dead are safe from its grasp, with morgues and gravesites changing their contents to better hide secrets better left unknown.
Decades, even centuries, of human history might be nothing more than a fabrication made to keep mankind ignorant... Or safe.

It is the Veil that keep Aspects subtle and memories of them fading. It does not, however, protect a foolish wizard from any immediate consequences.

Modern Life

It isn't easy being a warlock in our modern times, and Aspects doesn't make it any easier. Even when they don't mark someone as mystical, they always make someone stand out as... Strange. An outsider, someone who isn't quite like the rest of us.
The Veil smooth things over in the long run, but some Aspects put witches in danger just by drawing unwanted attention to them when they least want it. In old times, such attention could be fatal, with witch-hunters and superstitious mobs more likely to reach for a pitchfork than a selfie-stick.

In addition, the modern world has numerous options to help keep an Aspect hidden from view, though they seem resent such deception and sometimes bleed through attempted disguises.

Cleansing Aspects

After a while, the reactions gets old.

Aspects aren't always easy to live with, causing startled reactions or out-of-control twists to their Art. Some mages seek to cleanse themselves of Aspects, but it's an act easier said than done, involving a sort of surgery on their essence.. The most common and least desirable is to make a Pact with a Demon, whose expertise in soul-surgery makes such procedures easy (if not painless), but for a price most are... Uncomfortable with. Other being and other Pacts can remove or alter Aspects, while powerful patrons can imbue mages with Aspects by the pacts they sign.
No mortal magic can excise an Aspect from a mage, but they can hide them. Spells of illusion or shapechanging can alter or obscure an unwanted Aspect, while some supress them all-together. Most mages learn to live with their Aspects as just another part of who they are.