The Living Tunnel
Location: Pandemonium / Phlegethon
HEARSAY: Deep, deep amidst the howling bowels of Phlegethon, maybe twenty hard days travel out of Windglum, lies a place where the screams of madness are even louder than most. It’s whispered that the tanar’ri run a death-camp out this way, capturing and torturing any unlucky sod they stumble across. Others say that it’s a channel for the winds of madness that manifests themselves throughout the whole blasted plane. Of the few who have gone seeking the place; none have returned.
DESCRIPTION: Long ago, a tiefling necromancer, rendered completely barmy by the winds of Pandemonium, came to this area, driven by a desire to create a monument to his power of death. After years of intense work, his creation was finally finished. He had transformed a one-mile stretch of a relatively small tunnel (about ten feet in diameter) into a continuous Living Wall, a horror on a scale that had never before been seen in the multiverse. Infused with the madness of the plane, the tunnel immediately attempted to assimilate its creator, but the necromancer managed to escape from his creation—instead meeting his demise back in Sigil of all places, at the hands of an enraged vrock. Over time, the wall has grown by assimilating any unlucky sods that came close enough. It has now grown to some three miles in length.
Since its creation, the Living Tunnel has absorbed a good deal of barmies, but more significantly, it once engulfed a whole platoon of vrocks who were headed to the Blood War. As a result, the Living Tunnel has become virtually invincible, since it has gained many of the spells and powers of all those bodies it has absorbed. Further details would be pointless; suffice to say the Tunnel is likely a match for an army of Odin.
Were this the Abyss, the Tunnel might have been destroyed by enraged fiends, or pressed into service as a weapon. Were it in Mount Celestia, a host of devas would have sacrificed themselves to smite it as it struggled into its first consciousness. But this is Pandemonium, and nobody cares that such a monstrosity has been created because here… well, because nobody just plain sodding cares about anything here.
SPECIAL FEATURES: The walls of the Living Tunnel are littered with (indigestible) golden coins and the possessions of countless fools who have happened upon it. A berk able to clean up the whole bunch could be rich beyond their wildest dreams. Other than that, the Tunnel is more than happy to oblige a berk looking to spend the rest of their existence amalgamated into a bunch of barmies all trapped in its carnivorous walls.
HAZARD RULES FOR PATHFINDER 2e (click to expand)…
Devouring Tunnel Hazard 15
Unique | Complex | Environmental | Pandemonium
Stealth +10 (expert) to notice embedded bodies in the wall and realise it the wall about to attack
Disable DC 43 Athletics (master), Crafting (master), or Dungeoneering or Engineering Lore (master) to brace the tunnel to prevent it from engulfing prey until the end of the creature’s next turn. The DC of the flat check for this round (see Routine) is increased by 4 on a success, or by 8 on a critical success. Increasing the flat check DC to 21 or higher stabilises the tunnel, ending this hazard.
Devouring Engulf [reaction] Trigger A creature within the living tunnel takes a Move action other than Step or a successful DC 30 Sneak check; Effect The tunnel trembles and writhes, becoming difficult terrain within 30 feet of the movement; creatures on this difficult terrain take a –2 circumstance penalty to attack rolls, AC, and skill checks. The hazard rolls initiative.
Routine [1 action] The GM rolls a DC 9 flat check to determine if the tunnel attacks, increasing the DC as listed above. On a successful check, claws attack, blood and acidic mucus sprays everything within the area of difficult terrain, providing concealment and dealing 3d6 slashing and 3d6 acid damage to 1d4 randomly chosen targets (DC 35 basic Reflex save; on a critical failure, the creature is knocked prone). On a critical success of the flat check, the effect is the same, but the tunnel deals 6d6 slashing damage and 6d6 acid damage to 2d4 randomly chosen targets instead (DC 35 basic Reflex save; on a critical failure, the creature is restrained by grasping claws until freed [Force Open DC 38, Escape DC 35]).
Additional challenges could be added by introducing monsters to this hazardous environment, such as Giant Crawling Hands (CR5), or Unrisen (CR11).
SUGGESTED STAT BLOCK FOR AD&D 2e (click to expand)…
The Living Tunnel has grown to become at least a 60 HD creature. Living Tunnel: AC -5; MV nil; hp 651; THAC0 3; #AT uncountable, at least three hundred, but only eight attacks per area; Dmg 1d6 (x8) or by unique weapons (DM choice); SA vrock special abilities; SD vrock special abilities, hit only by magical weapons; MR 35%; SZ H (now ten miles long); ML Fearless (20); XP 250,000 (or more, as the DM rules).
Source: Dave King and Jon Winter-Holt. This homebrew idea was inspired by the Living Wall of Ravenloft [ 2e | 3e stats]. Pathfinder hazard based on the Collapsing Structure stats for the kaiju Ebeshra, Monsters of Myth [PF2e] p40