The story of 90 Has No Secant includes a very deep mythology of its own, even apart from its proposed sequels. The following is an overview of some of those elements.
Main article: Meshaluta
Meshaluta was not initially ruled to be a real entity; but just part of Eva's dream. She would eventually evolve a more significant role as story development went on. Frequent symbolism suggests that the hag's ghost is haunting the Rintels throughout, but her exact history and the fullness of her motives (and her power) are not revealed until sequels.
Meshaluta, in order to taunt her victims, will sometimes warn them poetically in a dream of things they should watch out for right before she kills sends her minions (or a fluke of nature) to kill them. She often recites the poems in an overly dramatic manner, including parodying the Weird Sisters in Macbeth. Eva's dream contains the following warnings:
Woe, oh Woe! For Nature is a-mess with self and style!
Take cheese, take crackers;
All the magnet, give sway!
Puppy sandals and snail shoes and pitiful day!
There's a bus outside; grab it;
You just keep wasting time!
Hear the lamps! See the wind!
Give the hourly chime!
NOW IT'S YOUR TURN!!!
- Woe Oh Woe: This line is repeated under breath by an old woman reading a newspaper in the LaFoe Airport.
- Nature A-Mess: Nekoda and the magnetic storm's paranormal behaviors.
- Cheese and Crackers: What the Rintels primarily had for breakfast that morning, early as nobody could sleep. Lenny also desires to eat some.
- Magnetism: The magnetic storm that causes the household equipment to act up and attempt to kill the Rintels.
- Puppy Sandals and Snail Shoes and Pitiful Day: References the puppies on a pair of Mandy's old sandals, being stored in the upper bedroom closet of the house. Curiously, this same basement becomes infested with snails, much to Lenny's horror. The "pitiful day" also destroys the Landana cruise ship, and scrap metal from the wreckage flies through a window and nearly impales Lenny.
- School Bus: A school bus crashes through the roof of the utility room.
- Grabbing the Bus: This is how the Rintels rescue themselves when Nekoda starts sending debris and rain into the utility room. The old woman with the newspaper also comments about a boy killed during an incident involving a school bus, which was mentioned in the paper.
- Hear the Lamps: Electronic devices begin to engage in eerie behavior, including strange noises.
- See the Wind: Flying debris that can kill the Rintels (or the burglars in their house.)
- Give the Hourly Chime: The grandfather clock in the living room, which chimes when the magnetic storm expires.
- "Now It's YOUR TURN!!!": Someone in Eva's family unit is marked for death.
Main article: Hurricane Nekoda
Hurricane Nekoda (and its predecessor Mahalia) gets its name from an obscure Bible verse. "Nekoda" is the name of a temple servant listed in Nehemiah 7:50. The name means "white-washed wall," which can translate as either "clean slate" or as "treacherous." As Meshaluta learns, Hurricane Nekoda makes for an unpredictable ally for her agenda.
In keeping with how the magnetic storm works, inversion of the normal properties and behavior of energy waves becomes a recurring theme. The oscilloscope in the utility room is able to turn itself on just by Tom motioning it to in his mind. Once on, the oscilloscope depicts "broken sound" as a constantly-moving secant graph on its screen. In cooperation with the magnetic storm, the eye of Nekoda temporarily becomes a pathway to time travel. This leads to a space shuttle and crew traveling backwards in time and crashing in a desert. Tom witnesses this in mid-air while he is petrified and his body begins to dematerialize.
Meanwhile, Mandy is attacked by a ghost that is assumed to be that of Jack the Ripper. It takes the effort of Rick unplugging the oscilloscope and Tom snapping out of his trance to send the ghost back into its wormhole before it can decapitate Mandy. The Ripper Ghost is portrayed as having ragged hair, wearing mostly black, skeletal hands, and an indefinite black mass for a head with no face save for two bright-glowing white eyes. Body parts that come into direct contact with the ghost become invisible, save for the bones underneath.
As with most of Classic Gerosha, 90 has a slightly altered US geography from real life. The Rintels live in a small town called Murian Twp., which is located in approximately the same location as the real-life Grand Isle. The LaFoe Airport is inspired by the South Lafourche Leonard J. Miller and Gerald R. Ford International airports. While the Rintel house is said to be on Plum Lane, there is little indication that Plum Lane in Murian looks anything like Plum Lane in Grand Isle.
Even the architecture of the family's house was cause for some concern. The original plan for the house was to have it include a basement for the family to hide inside of. This was replaced with a utility room when research of the Louisiana water table ruled out all possibility for the family to have a basement. Even so, their house is built in a manner in the conceptual art that is inconsistent with typical Louisiana architecture. This is because the original inspiration for its design came from a small house in Kenosha, Wisconsin.