Landscape and AtmosphereThe Desert: It is a perpetual night world covered in vast, seamless white sand dunes.The Trees: Scattered across the desert are crystalline, dried-up structures that look like dead trees, but they are actually made of quartz.The Moon: A giant, inverted crescent moon hangs permanently in the dark sky.Reishi Density: The atmosphere is packed with an incredibly high concentration of ambient Reishi (spiritual particles). Because of this, smaller or weaker Hollows can survive effortlessly without ever needing to hunt or consume.Gillian (The Base Menos)How They Look: Giant, identical tower-sized monsters wearing long, black flowing cloaks. They have a white mask with a very long, pointed, bird-like beak. Their tongues are exceptionally long and pointed.Their Behavior: They are completely mindless, slow, and act entirely on instinct. They roam around in massive herds like zombies and lose all the individuality they had as normal Hollows.2. Adjuchas (The Mid-Tier Menos)How They Look: Smaller than Gillians (roughly human to elephant-sized), but highly unique in appearance. They take on distinct animalistic or mythological forms, such as panthers, lizards, birds, or bulls.Their Behavior: Highly intelligent, capable of speech, and deadly fighters. To maintain this form and avoid devolving back into a brainless Gillian forever, they must constantly hunt and eat other Adjuchas.3. Vasto Lorde (The Ultimate Menos)How They Look: Extremely small, roughly the exact size of a normal human. They lose their animal features and become completely humanoid, usually retaining a fraction of a mask on their face or head.Their Behavior: The absolute pinnacle of Hollow evolution. Their numbers are extremely rare, and their combat power is said to vastly surpass that of an average Soul Reaper Captain.What Happens: If a mask is cracked or partially broken by a Quincy, a human, or another Hollow during a fight without killing the Hollow outright.The Result: The mask is a Hollow's ultimate defense and the core container of its spiritual energy.Minor Damage: If a piece is chipped off, it causes immense physical pain and can permanently stunt their evolution (for example, if an Adjuchas loses a piece of its mask, it can never evolve into a Vasto Lorde).Key Rules of EvolutionTo understand how this hierarchy functions, three critical rules govern their transformation:Cannibalism: Evolution is fueled strictly by devouring other Hollows. Base Hollows must group up and consume each other in mass numbers to trigger the fusion into a Gillian.The Regression Curse: Adjuchas live under constant threat. If an Adjuchas does not continuously consume other Hollows, its personality will be permanently swallowed by the other souls within it, regressing it back into a mindless Gillian forever.The "Bite" Rule: If a piece of an Adjuchas's body is eaten by another Hollow, that injured Adjuchas loses the ability to ever evolve further. Their growth is permanently stunted