The Veil

The last thing you should trust is your memories.

Even now, with cameras watching every move and corporations monitoring every twitch of their consumers' life, Magic remain secret, just as it have through the ages. It is a cosmic force of self-enforcing secrecy that draws the blinders over the eyes of humans, shrouds machinery, and manipulates history. Magicians call this force the Veil; blinding mankind to the horrors and complexities of truth.

The Veil Is Drawn

All right, Beatrice, there was no alien. The flash of light you saw in the sky was not a UFO. Swamp gas from a weather balloon was trapped in a thermal pocket and reflected the light from Venus.

— Agent Kay, the Men In Black movie

Insidious and pervasive, the Veil works to cloak the secrets of the world from the uninitiated by worming its way in any way necessary. It changes memories, alters objects, and has shown itself more than capable of adapting to the ever-changing march of technology. Human minds, always fallible, are the first thing to fall, and memories of what happened falter before the first statement is given to the cops. First, it's subtle. Spells and whiz-bang relics are remembered as firearms or other modern weaponry, while ghouls and goblins are replaced by muggers and murderers.

by http://www.tribalartasia.com/

Records aren't any safer, with written words changing - and who's to say what was really on that police report, anyway? Things get lost in the shuffle, left to gather dust in storage, or always seem to fall in the hands of those too lazy or inept to really care about it. Through coincidence and an unfortunate sequence of events, things strive to remain unknown.
Technology suffers similar fates. Recordings change or get lost, internet uploads fail, files are corrupted, and memories of what was really on them start to slip too. Once the Veil begins to close, it's difficult to stop, and the changes it makes grow, sowing doubts and forgetfulness. Photos that might've once showed that monster clear as day just show a wild animal or indistinct shape.

Then there's the big question: is the Veil sentient? Some argue that its alterations are too calculated to be simple gravity of secrecy - thermodynamic, they say, does not display as much of a sense of ironic humor as the Veil.
Others are less convinced, but maybe they've been duped by it, too.

From there, the Veil works backward in time and space. As time goes, the change reacher further back and twists ever more things to fit the corrected narrative. Recollections about discrepancies fade and doubts fade into obscurity. More and more, the change creeps in deeper and deeper. Once its barbs are in, the Veil never lets go. History changes retroactively, and what was once an exciting new conspiracy theory bleeds dry into gray disinterest.
There's no telling just how far back into history the Veil has reached to cloak accident and indiscretion - not even magi know. Decades, even centuries, of human history might be nothing more than a fabrication made to keep mankind ignorant... Or safe.

by http://www.tribalartasia.com/

Awareness

Witch, warlock, wizard - no matter what they're called, they are all separated from the rest of mankind by what they call awareness. Not just theoretical knowledge or a belief, awareness is a mystical state of being - a deep, primitive instinct that tells you that the world isn't what it seems. The Aware aren't affected by the Veil - presumably, they're already in on its secrets.

The Mandela Effect

For all its frailties, the human mind is a stubborn thing, and not everyone forgets like they should. Sometimes, entire parts of history diverge as people fall on different sides of the Veil's manipulation, giving rise to the Mandela effect.
It isn't clear exactly when this happens - if it's a quirk or flaw in the system, or some event too egregious to hide fully - but they're happening more and more often.

by Rock Cafe.info

That's not to say a witch can just go around doing as she pleases, friend. If you kill someone, they're still dead, and the electric chair doesn't care what kind of spin the narrative takes there. You never know exactly what it's going to do, but if you think it's there for your sake, you'll be remembered for your stupidity if nothing else.

— Tsu the Tea-Witch