The Heart of Geode-Null
The Heart of Geode-Null is a sentient tectonic core that serves as the architect and master of the lightless depths. It treats the surrounding miles of stone as its own body, reshaping corridors, manifesting mineral guardians, and weaving spells through the very air. To enter its chamber is to step inside a god-sized brain made of obsidian and pulsing amethyst.
The Heart of Geode-Null
Defenses
Detection
“A massive, levitating octahedron of faceted diamond and deep-space obsidian, thirty feet in height. It is surrounded by orbiting rings of pulverized stone and glowing ley-lines that hum with a sound like grinding tectonic plates. The walls of the cavern rhythmically expand and contract like lungs.”
Standard Engagement
Entering the Heart Chamber or attempting to cast a spell of 6th level or higher within the Geode-Null cavern system.
On initiative count 20, the Heart reshapes the room (Spatial Reconfiguration). On initiative count 10, it manifests an offensive response (Looming Annihilation).
The Heart is the core of the dungeon; it resets daily at dawn unless its logic is completely rewritten.
The Heart rotates the cavern. Each creature must succeed on a DC 32 Dexterity saving throw or take 100 (10d10 + 45) bludgeoning damage as the walls crush inward, falling 60 feet in a random direction as gravity flips. On a success, the creature finds a temporary foothold and takes half damage.
The Heart casts a modified Meteor Swarm or Power Word Kill (Save DC 35). It can also choose to manifest two CR 20 Earth Elementals within the chamber as a bonus action.
Within the cavern, the Heart can use its reaction to counterspell any magic cast by an intruder (Auto-success for levels 1 to 9).
At the start of its turn, the Heart regains 100 hit points if it is in contact with the ground or its levitating orbit of stones.
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