Izanami's true form is a body in a state of very severe decomposition, so much that she is practically a living skeleton. It is unclear whether the long, dark hair is truly a part of her body that hasn't decomposed as badly or rather just a remnant of her fake illusion under which she had appeared to Yato. In all of her forms, Izanami is seen wearing a long dyed kimono with flower motifs over a plain white kimono.
Whoever casts their eyes on her, Izanami is seen in the likeness of the person they feel most comfortable with: In Yato's case, she takes the appearance of Hiyori, in Ebisu's case she takes the appearance of an old lady who runs a certain western food shop called "The Olive Tavern". However, when Izanami loses her composure, the illusion maintaining her different appearances begins to fade; eventually breaking completely to reveal her true form.
It is implied that Izanami has a sweet and gentle, yet savage and barbarous nature. She has been consumed by her loneliness for a very long time, which makes her sad, impulsive, temperamental and irrational, especially when someone goes to the underworld and doesn't want to be her friend. Her pursuit is relentless, getting angry whenever she loses track of them or they run away.
Izanami seems to be aware of what form she takes depending on the person, flirting with Yato in Hiyori form but didn't do so for Ebisu, though she could just be observant and was able to tell Yato was attracted to her but not Ebisu. She resorts to drastic measures to make others stay with, such as having Yato and Ebisu fight over who would get to leave and chasing after them with her beldams.
Interestingly, Izanami didn't care about having any of the Shinki or Bishamonten be her friend, both of which she fed to her beldams: The Shinki are pure souls, so they would most likely die since pure souls can't live in the underworld, which would explain why she wasn't interested. She might also prefer male company, deciding to feed the war goddess to her beldam rather than try to befriend her.
Skills & Abilities
Phantom Summoning: Izanami is able to create the Mandates of Hell (Phantoms Brushes), which she uses to summon phantoms without chanting or affixing a mask. While unseen, it is implied she can create masks with the brushes too. Unlike most gods, Izanami doesn't sustain blight in the process. On these moments, her eyes look like two concentric circles with a black dot for a pupil inside, a similar patter being replicated on the masks and bodies of phantoms she has evoked.
Underworld (Yomi) Control: Through the halo with spreading rays, Izanami is capable of connecting to the Yomi infrastructure. This allows her effortlessly find others and prevent their escape by sealing all the pathways out. Izanami is the commander of countless hordes of flesh-hungry Yomi entities (Yomotsu-hisame), entities looking like young naked females with long dark hair who stay under the Yomi waters when she is calm. When she is angered, they will hunt down and constrict victims, taking occasional bites or offering rotting foods of the Underworld - which renders one unable to ever leave the realm.
Izanami's hair: Her personal weapon with some tracking capability. Its grip affects gods and their Shinki, leaving them unable to fight back.
In Japanese Lore
Izanami (イザナミ, historically 伊弉冉尊 or 伊邪那美命; lit. "She Who Invites"), along with her husband Izanagi (イザナギ, historically 伊邪那岐; lit. "He Who Invites") belongs to the seventh generation of gods to be spontaneously created according to the Shinto creation myth. Since they were the first gods capable of reproduction, Izanami and Izanagi were tasked with making order in the chaos that was the universe and inhabiting it. They separated the world into the heavens (Takamagahara), the underworld (Yomi) and the "earthly realm" (Ashihara-no-Nakatsukuni).
After these events, the couple descended to the earth in order to begin inhabiting it. The first offspring Izanami bore was a deformed child called Hiruko (蛭子; lit. "leech child") - later identified with Ebisu - who was cast to sea in a boat. The children that followed were gods that took the form of islands, making land rise from the sea - creating Japan. Her last child was the fire god Kagutsuchi (カグツチ), who killed her at birth, sending her to Yomi, the realm of the dead.
After killing Kagutsuchi in a fit of rage, Izanagi sent for Yomi in order to retrieve his beloved wife. When he finally saw her though, he found out that Izanami had already eaten from the food of the underworld, forbidding her from ever leaving. The sight of her decomposing body terrified Izanagi and made him flee, causing an enraged Izanami to send the fiends of Yomi after him in turn. After finally escaping from Yomi, he sealed its entrance (Yomotsu Hirasaka) with a boulder
- Being bound to the underworld - an environment where uncorrupted souls cannot survive - Izanami is, in theory, a goddess with no means to ever procure Shinki.
- Unlike other gods, Izanami cannot die because of her position as ruler of the underworld, so she will continue on living as long as life and death exist.