Underground Cavern Beneath Rex Tree

Summary

The Underground Cavern Beneath Rex Tree is a hidden subterranean complex located directly beneath The Rex Tree in the town of Rex Tree. The cavern system descends 20-30 feet below ground level through a winding tunnel that opens into a large central chamber with multiple branching passages. The space serves as a ritual site for The Masked Cultists, who conduct ceremonies to The Sniff Lord at a Stone Altar heaped with food offerings.

The network consists of multiple tunnels and chambers connected by portcullises controlled through stone button mechanisms. Safia describes the layout as being "like a rabbit warren" similar to Watership Down. The entrance can seal shut, trapping those inside, and the cavern's ceiling allows greasy black smoke from torches to seep upward through the rock while the roots of The Rex Tree penetrate down from above.

Description

The main tunnel descends from the base of the Rex Tree, measuring approximately 7-8 feet tall and 5-6 feet across. The passage walls consist entirely of earth and stone rather than wood, despite originating from within the tree trunk itself. As one observer notes, "it doesn't even look like wood. Like, it doesn't look like part of a tree. It just looks like earth and stone."

The tunnel winds downward for 20-30 feet before opening into a large central cavern. Multiple other tunnels of varying sizes and shapes curl off into darkness from this main chamber. The Rex Tree's roots penetrate through the cavern ceiling, creating a direct connection between the underground space and the massive tree above.

The ritual chamber is illuminated by torches stuck into the ground on poles and braziers that provide flickering flame light. The torches produce "greasy black smoke" that fills the upper portion of the cavern and seeps upward through gaps in the rock. The atmosphere is thick with this smoke, which creates a hazy environment throughout the space.

At the center of the main cavern stands a rough Stone Altar piled high with offerings: vegetables including peppers and potatoes, fruits such as apples, leafy balls of vegetables that may be endives, and numerous acorns. The altar serves as the focal point for the rituals conducted by The Masked Cultists.

The warren-like network contains at least three separate tunnels leading to unknown areas. Multiple portcullises divide the passages, all controlled by stone button mechanisms. A ramp leads up and out of the ritual chamber toward the surface. Something large dwells in the darkness beyond one portcullis, responding to sounds with rumbling bellows that grow closer when disturbed.

The acoustics are excellent for echolocation. When Safia shapeshifts into a bat and begins making echolocation noises, the sound is "surprisingly loud in this cavern" with "sound waves bouncing off the walls." This shrieking sound echoes throughout the cavern and down through the tunnels into the darkness below.

History

Session 3

The party discovers the tunnel entrance while investigating The Rex Tree. Safia transforms into bat form and uses echolocation to scout ahead, screeching to send sound waves reverberating through the passage. Her sonar reveals the tunnel's full extent: "Off this tunnel show you a shape that like the tunnel that you're in curls down down into the earth. Probably 20 or 30 more feet down and then it opens into a large, large cavern at the bottom that has several other tunnels that run off from it."

As Safia explores using her echolocation, she detects movement within the cavern but cannot get a clear picture of what is moving. The party proceeds deeper into the tunnel system, where they discover the torch-lit main chamber with its Stone Altar and food offerings.

Upon entering the caverns, the party encounters 4-5 Robed Cult Figures with hoods pulled up over their faces. The Dog-Masked Cultist stands behind the altar and grabs a broom, attempting to jam the handle through the portcullis to poke Vasso, Katniss, and Sucks down the tunnel.

Safia transforms into a giant bat, with wings flapping and beating the flames on the braziers around the room, causing them to flicker and sputter. The bat's echolocation noises echo throughout the cavern and down through the tunnel, provoking a rumbling response from something deeper in the darkness. Safia grabs a chalice full of water from the altar and splashes it through the portcullis during the confrontation.

The cultists lose control of the situation. They grab sticks and torches and attempt to attack the giant bat. The masked entourage becomes so terrified that they run up the ramp and out of the chamber.

The situation becomes dire when the entrance seals behind the group, trapping them inside the tunnel system. The party becomes further trapped in the complex when Safia opens one portcullis but inadvertently bars the door at the top of the tree. The Masked Cultists refer to these spaces as "the caverns" and use them as a location for trials or sacrifices to The Sniff Lord.

Notable Features

Sealed Entrance: The tunnel entrance features a wooden portcullis mechanism that can trap visitors inside by sealing shut behind them
Multiple Passages: Several tunnels of different sizes and shapes branch off from the main cavern into unexplored darkness, forming a warren-like network
Living Tree Connection: The Rex Tree's roots visibly penetrate through the cavern ceiling, maintaining the connection between underground and surface
Stone Altar: A rough stone altar heaped with vegetable, fruit, and acorn offerings serves as the ritual focus point
Braziers and Torches: Torches on poles and braziers provide illumination while producing thick greasy black smoke that fills the ceiling space
Smoke Ventilation: The smoke seeps upward through gaps in the rock ceiling, suggesting natural or cultivated ventilation paths
Portcullises: Multiple gates controlled by stone button mechanisms divide the passages
Ramp Access: A ramp leading up and out of the ritual chamber toward the surface
Echo Chamber: The cavern's excellent acoustics allow Safia's echolocation to map the full extent of the tunnel system, with sound waves bouncing off walls and echoing down tunnels
Dark Passages: Tunnels extending deeper underground where something large dwells that responds to sounds with rumbling bellows