I. Tiers of the Blade Wielders and Sword Maidens
Because Blade Spirit and Blade Wielder, Sword Soul and Sword Maiden, stand in strict one-to-one correspondence, no specific distinction is drawn between the two sides here beyond what they are called.
Embryo Tier: three Realms in all. Ranked from low to high by the depth of fusion with the Blade Spirit or Sword Soul and by sheer strength, they are the Body-Forging Realm, the Soul-Fusing Realm, and the Sublimation Realm.
The mark of crossing into the Soul-Fusing Realm is that the wielder's own body begins to drift toward the look of the transformed state, as with Bai Wuxie's crane-white hair over a child's face. This Tier grants only one signature Blade Art or Sword Art.
Sheath Tier: once power has built up to a certain degree, the finest of the Embryo Tier's Sublimation Realm can condense a destined blade sheath or sword sheath, and their survivability and protection rise sharply.
By the completeness and strength of that blade sheath or sword sheath, and by how tightly the Sword Intent or Blade Intent has been condensed, it divides from low to high into the Sheathed Realm, the Drawn Realm, and the Sheathless Realm.
The Sheathed Realm grants a second signature Blade Art or Sword Art. The Drawn Realm allows Blade Intent or Sword Intent to be extended from oneself onto others. The Sheathless Realm allows the sheath to be released and a second-stage transformation.
Vessel Tier: not yet unlocked. To be filled in as the story advances.
Soul Tier: as above.
II. Tiers of the Blade Demons and Sword Fiends
These stand in one-to-one correspondence with the Blade Wielders and Sword Maidens. They originate in the corruption of the Demon God, the incarnation of human evil, and of the seven Innate Demon Kings enthroned beneath him. A Blade Wielder or Sword Maiden steeped in and driven by his or her own malice will irreversibly, by degrees, fall into a Blade Demon or a Sword Fiend. (In special cases, such as one person holding Twin Blade Spirits or Twin Sword Souls, the fall can be deliberately held to less than halfway, making a Half-Demon or a Half-Fiend.)
First-Fall Tier: corresponds to the Embryo Tier of the Blade Wielders and Sword Maidens. A Blade Demon turns into a non-human shape, an animal or something similar; a Sword Fiend keeps human form but shows the first traces of the beast.
Quasi-Demon Tier: corresponds to the Sheathed Realm of the Sheath Tier. The Blade Demon's core is better hidden, while the Sword Fiend's beast traits sharpen and the weak point at its core shows a little more clearly.
Lesser Demon Tier: corresponds to the Drawn Realm of the Sheath Tier. The Blade Demon takes on a certain tendency toward human shape; the Sword Fiend's beast traits slip steadily out of control.
Greater Demon Tier: corresponds to the Sheathless Realm of the Sheath Tier. The Blade Demon gains the ability to turn itself human for a short while, while the Sword Fiend can go fully beast for a short while and come back to human form.
Quasi-Demon King Tier: not yet unlocked. To be filled in as the plot develops.
Acquired or Innate Demon King Tier: as above.
False Demon God Tier: as above.
Demon God Tier: as above.