The Mist

“Okay, that’s extremely cool,” I admitted. “But what if a mortal sees me pulling out a sword?”
Chiron smiled. “Mist is a powerful thing, Percy.”
“Mist?”
“Yes. Read The Iliad. It’s full of references to the stuff. Whenever divine or monstrous elements
mix with the mortal world, they generate Mist, which obscures the vision of humans. You will see
things just as they are, being a half-blood, but humans will interpret things quite differently.
Remarkable, really, the lengths to which humans will go to fit things into their version of reality.”
(The Lightning Thief, Chapter 10)

“Percy,” she said, “have you ever looked at Tyson closely? I mean ... in the face. Ignore the Mist,
and really look at him.”
The Mist makes humans see only what their brains can process ... I knew it could fool demigods
too, but...
I looked Tyson in the face. It wasn’t easy. I’d always had trouble looking directly at him, though
I’d never quite understood why. I’d thought it was just because he always had peanut butter in his
crooked teeth. I forced myself to focus at his big lumpy nose, then a little higher at his eyes.
No, not eyes.
One eye. One large, calf-brown eye, right in the middle of his forehead, with thick lashes and big
tears trickling down his cheeks on either side.
“Tyson,” I stammered. “You’re a ...”
“Cyclops,” Annabeth offered. “A baby, by the looks of him. Probably why he couldn’t get past the
boundary line as easily as the bulls. Tyson’s one of the homeless orphans.” (The Sea of Monsters, Chapter 4)

“My main role as a goddess is maintaining the Mist, the magical barrier between the Olympian and mortal worlds. I keep those two worlds apart. When mortals do get a glimpse of something magical, I come up with happy alternatives for them to believe in. Alabaster also has power over the Mist. I’m sure he showed you some of his creations—symbols that can been turned into solid objects.” (The Demigod Diaries, Son of Magic)