Gelatinous Cube

Gelatinous Cubes of Grizburg

 

Appearance

The gelatinous cubes of Grizburg shimmer with an unnatural radiance, lit from within by dissolved alchemical waste and glowing fragments of metal. Their translucent bodies reveal half-digested bones, chains, and the outlines of victims locked in perpetual scream. They slide silently, quivering with acidic hunger, like living lanterns drifting through darkness.   ---

Origins

Many believe they formed when alchemical runoff from Rustwater mingled with Zothra-Khaar’s ichor deep beneath the city. Some scholars argue they were once tools, experimental waste disposals for the Barons’ vaults, which outgrew their purpose. Now, they wander freely, devouring all they touch and leaving nothing but smooth, corroded stone in their wake.   ---  

Habitat

They thrive in the sewers, cisterns, and collapsed tunnels beneath Grizburg. At night, some cubes seep up into alleys, their faint green glow mistaken for lanternlight until too late. In the Whispering Depths, they drift like phantoms, lurking in choke points and ambushing explorers with their engulfing advance.   ---  

Ecology

Gelatinous cubes are perfect predators: silent, patient, and indiscriminate. They consume flesh, wood, and steel alike, dissolving all but the most stubborn relics. These items often remain suspended in their mass, tempting treasure hunters even as the ooze slithers forward. Their trails corrode stone and metal, leaving tunnels pitted and unsafe.   ---  

Behavior

Despite their mindlessness, cubes display unsettling cunning. They linger in places where shadows and hunger intersect—under trapdoors, behind gates, in flooded streets. Once prey stumbles close, the cube lunges with gelatinous precision, engulfing its victim in a smothering embrace. Few realize they are trapped until the acid burns away breath.   ---  

The Whispering Depths Connection

Cultists of Zothra-Khaar worship the cubes as fragments of the god’s stomach, calling them “the Digesters.” Offerings of flesh and blood are poured into their quivering forms, and the faithful read prophecy in the way bones dissolve within. Some claim vast “cathedral cubes” dwell far below, each containing relics of forgotten ages.   ---  

Use by Factions

The Rust Barons weaponize them as vault guardians, luring cubes into storage chambers and starving them until intruders enter. Assassins sometimes release them into alleys, letting the ooze consume corpses and evidence alike. More daring smugglers have even hidden goods inside cubes, training them to spit the treasure back out for the right command.   ---  

Cultural Role

In Grizburg folklore, cubes are called “Street Lanterns.” Children are warned to never follow strange green glows in foggy alleys, lest they walk into acid. Miners claim cubes are omens of collapse: if one appears in a shaft, the stone itself is cursed to give way. The bravest gamblers tell tales of watching cubes drift through vaults, daring one another to retrieve the floating relics.   ---  

Legends

The Vault Lantern is the most infamous tale—a cube said to haunt the ruins of a Baron’s treasury, glowing with the light of gold and jewels still drifting within. Another story tells of a cube so large it filled an entire cistern, swallowing barges whole when floodgates opened.   ---  

Threats to the City

Beyond their acid, cubes threaten Grizburg’s stability. They corrode bridges, dissolve supports, and hollow sewers until collapse is inevitable. A swarm of cubes loose in Rustwater could consume entire districts before the Barons even admitted they existed. Their silence makes them doubly deadly, as no warning precedes the burn.   ---  

Behavioral Oddities

Some cubes glow with strange colors—violet, crimson, or cobalt—depending on what alchemical waste they consumed. Others “echo” with swallowed voices, bubbling cries carried in air pockets inside. The strangest are said to linger before statues or shrines, as if worshiping before consuming.   ---  

Adventuring Hooks

• A Baron hires exterminators after a cube infests his treasure vault. • Smugglers pay to capture and herd a cube through rival warehouses. • A cube glows violet, revealing a magical relic floating within. • In the Depths, explorers encounter a cube the size of a cathedral, pulsing with prophecy.   ---  

Closing Words

Gelatinous cubes in Grizburg are not accidents of nature—they are reflections of the city itself: silent, corrosive, patient, and inevitable. In the smog and shadow, their glow is a reminder that even light can kill. See full stats on D&D Beyond