The Spiral of Madness/Incarnations can be classified very easily, they go from Tier 9 to Tier 0, and each Tier has a unique name based on the Spiral, alongisde a tied Ability earned within that Tier. Incarnations, materialized Entities from the Spiral are born every time a Spiralwalker reach a new Realm, making it four incarnations per Spiral.
Spiral Tiers
Origin Realm, The Lost (Tier 9–7): Awakening phase. The Fantasy begins as one loses themselves.
Adept Realm, The Fallen (Tier 6–4): Powers deepen and become thematic. The Awakened fall too far into their Fantasy to return.
Elite Realm, The Enlightened (Tier 3–1): Near-divine mastery. Reality bends around the Incarnation.
Mythic Realm, The Worshipped (Tier 0): The Incarnation becomes a living archetype, rewriting the world with their Fantasy.
Each Spiral has their own unique way of growing and advancing, and often have special requirements tied to the madness within the Spiral, for example, the Spiral of Ashen Wyrm needs the user to bathe in the ashes of their loved ones to advance to Tier 8, the Spiral of the Desecrated Soul needs the user to rise one hundred undead, and so on.
Some can be more complicated than others and not all spirals are made equal, some are clearly stronger, but also come with bigger drawbacks or more resource requirements.
Incarnations.
A deeper explanation would be that Incarnations are Spirits within each Spiral, they can materialize at will, feed on their master's Fantasium and Emotions, and can attack and defend them. Incarnations cannot die, when they are destroyed, they go into slumber and after some time, they will revive.
Incarnations come in all shapes and forms, but most of them are metallic or made of stone, some can be ghost-like, but not many ever show any kind of fleshy appearance, and are often cold, emotionless, and don't speak. Louis' Incarnation, the Gravewalker, is an anomaly because of how smart it is compared to most Incarnations.
Incarnations grow alongisde their master and their Spiral Tiers, but because each Spiral has Four Incarnations, it's quite obvious that the first few ones may grow a little "obsolete" when compared to the strongests. However, a good Spiralwalker learns how to use all of their Incarnations and their unique abilities effectively.
Incarnations can also channel their master's skills, spells, and even learn how they move and mimic their weapon techniques or manners the stronger the bond between Incarnation and Master are. But they still tend to be mostly silent, looming entities that only watch in silence awaiting commands.