Mist

The Mist is a supernatural force controlled by the goddess Hecate that twists a mortal's sight from seeing monsters, gods, Titans, and various other mythical creatures and supernatural occurrences by replacing them with things the mortal mind knows about and can comprehend. This includes seeing magical weapons, as Percy's sword Riptide sometimes appears to mortals as a rifle or a baseball bat. Some humans can see through the Mist as well, including Rachel Elizabeth Dare, May Castellan, Sally Jackson and possibly, Esperanza Valdez.

Description
It is Hecate's job to make sure the mythological events are replaced with visions of normality. Under the influence of Mist, a mortal would see gods or monsters as ordinary humans or animals, and supernatural objects also become commonplace items. Demigods and mythical creatures such as Satyrs can all see through the Mist at most times (though sometimes the Mist is strong enough to fool even demigods), and manipulate it to a certain degree, with Thalia, Hazel and Chiron as examples. Although the true extent of the Mist's power is unknown, we see in The Demigod Files that it can make Mrs. O'Leary look like a poodle, yet satyrs and centaurs must disguise themselves as opposed to going around as is. Mist is strong enough to wipe from the memories of both the Greek and Roman demigods about the existence of each other. Thalia is able to manipulate the Mist, along with Chiron and probably many others.

In the short story Son of Magic in The Demigod Diaries, the Mist is shown to be able to form into physical objects by Hecate and her children. Alabaster C. Torrington created an Imperial Gold sword, and a guardian from Mist called Mist forms, and Hecate created a Mist form body for the soul of Howard Claymore, who died to protect Alabaster. The Mist is also strong enough to distort the vision of humans enough that they don't even realize that hazardous and deadly things are happening to them. Dr. Claymore's friend, Burly Black, burned to death without realizing a thing.

According to Chiron in The Lightning Thief, the Mist is mentioned in the Iliad. It is not specified which part he is referring to, but Book XX of the Illiad mentions Poseidon pouring Mist over the eyes of Achilles to protect Aeneas. Book V also specifically describes Athena giving Diomedes the ability to see gods:

"And I've removed the filter from your eyes, which covered them before, so now you'll easily distinguish between gods and men."

After that, Diomedes injured Aphrodite in the hand when she was trying to rescue Aeneas.

Another story about Jason and the Argonauts on their quest to recover the Golden Fleece has Hera cover the group in a layer of Mist that makes it so no one notices them until they reach the palace of King Aeëtes of Colchis, Medea's father.

The Lightning Thief


The Mist is mentioned several times, normally hiding Percy's sword from mortal eyes. It also hides monsters, such as when the Furies attacked Percy and his friends on a bus, but the people only saw Percy attacking three old ladies. The Mist also hides most of Percy's fight with the god Ares, making their swords appear as guns to the police and also hiding Ares' appearance as a god. The Mist also hides Camp Half-Blood from the eyes of humans, as anything inside the Camp Borders appear as nothing more than a strawberry field.

The Sea of Monsters
The Mist made a group of Laistrygonian Giants appear as normal students until they showed their true form when they attacked Percy. The Mist also hid the fact that Tyson was a Cyclops until Percy looked directly at him. Later when given a quest into the Sea of Monsters, it is explained that there is a strong layer of Mist in the Bermuda Triangle, resulting in ships and plains getting lost inside it. Chiron later uses the Mist to make up a fake cover story to shift the blame away from Percy for the attack on the gym.

The Titan's Curse
Thalia Grace showed that she is able to manipulate the Mist, as shown when she snapped her fingers and a teacher thought they went to the school. Later, as the group climbed up Mount Othrys, Thalia explained that the top of the mountain had a very strong layer of mist. Percy then asked if she meant the magical kind or the natural kind, she explained that both forms were strong. This may also indicate the strength of the Mist in California due to the existence of Camp Jupiter in the vicinity (particularly San Francisco).

The Battle of the Labyrinth
The Mist is very strong inside the Labyrinth. It is strong enough to fool demigods into traps or to get them lost. Percy eventually had to ask Rachel Elizabeth Dare for help, as she was a clear sighted mortal and could see through the Mist in the maze.

The Last Olympian
The Mist hid Typhon's true form from the eyes of demigods and humans. Regular humans saw it as a freak storm system that was moving across the country toward New York City, although demigods such as Percy Jackson could see part of his form. However, Percy claims that he could have been driven crazy if he looked at Typhon for too long.

The Lost Hero
The Mist causes many false memories of Jason Grace with Piper McLean and Leo Valdez. However, their false friendship becomes a reality, with Piper's love interest with Jason eventually becoming true. It is also revealed how the gods used the Mist to divide the two camps.

The Son of Neptune
Even in Alaska, the land beyond the gods, the Mist is very strong. Hyperborean Giants live freely there, but most humans simply ignore them and act like they aren't there.

The Mark of Athena
The Mist is mentioned by Percy when the seven heroes land the Argo II in Rome.

The House of Hades
On the bequest of Hecate, goddess of the Mist, Hazel Levesque learns to manipulate the Mist in order to confront the sorceress Pasiphaë and the Gigante Clytius. She also uses her abilities with the Mist to manipulate the demigod Sciron.

Piper McLean finds manipulating the Mist to be very similar to charmspeaking; in order to perform both tasks, one has to show what their victim wants to see, not what he or she wants them to see.

Hazel uses the mist to bend the labyrinth to her will, making passages appear and tricking Pasiphae, making her believe that she fell into a chasm.

Mortals With Clear Sight

 * Rachel Elizabeth Dare
 * Sally Jackson
 * May Castellan
 * Ariadne
 * Maria di Angelo
 * Esperanza Valdez
 * Frederick Chase (possibly); he was able to attack monsters with Celestial bronze bullets in The Titan's Curse.
 * Some parents of demigods are able to see through the Mist, while others (like Tristan McLean) are unable to.

Percy Jackson: Sea of Monsters
Unlike in the series, where the Mist will blind mortals to anything relating to magic, the gods, or monsters, the Mist can be applied using a magical "spraying" object. However, the Mist itself does exist without the spray, which is shown when the gang visits the coffee shop and the mortals see the man at the kiosk with only two hands instead of eight.

Trivia

 * The Mist divided the Roman and Greek demigods for years - implicated by the strong presence of the Mist near Camp Jupiter and Camp Half-Blood.
 * Mortals who are a parent of a demigod usually have the ability to see through the Mist (like Sally Jackson), but not always (like Tristan McLean).
 * The Mist cannot only distort vision, but also creates false memories and suppresses real ones.
 * The Mist does not completely hide some of the physical features of Satyrs/Fauns, leading them to find numerous ways to disguise themselves.
 * The Mist distorts weapons, monsters, battles, places, and supernatural occurrences that are incomprehensible to mortal minds.
 * It is noted that Carter Kane saw flying horses near the Empire State Building or Olympus. It is unknown if the effects of Mist apply to him because he is a magician or it was really his imagination.
 * In The Stolen Chariot, a mortal child can see the horses that pull Ares' War Chariot. It is possible that she can see though the Mist.
 * Besides the children of Hecate, Thalia Grace and Hazel Levesque are the only two demigods known to possess the ability to manipulate the Mist. In fact, Percy Jackson has shown more than once that he is frustrated that he lacks the ability.