The Bismuth Tower

Written by Nuriochi

Looming above the dense forest canopy, the strangely angled and geometric tower gleams in rainbow hues in the setting sun. Moving closer, a keening thrum fills your ears. You can feel it in your bones. The tower has no entrance, until it suddenly does. A stair ascends into darkness, made of the same gleaming rainbow stone. The tower seems almost alive, inviting you in...

Purpose / Function

The Bismuth Tower stands alone on an island in the Emerald Sea. From it, a Githzerai rrakkmas ventures forth in their search for artifacts related to the return of the Illithid to this Prime Material plane. The tower provides foodstuffs, areas for cultivating crops and raising animals to feed those within, as well as a series of "menageries" where local humanoids and creatures are stored for study. The Githzerai also kidnap locals and store them in "psychic storage". This prevents locals who have spotted the hunting party from gaining information about the rrakkmas movements and plans.
The hook here could be anything from a larger campaign-stretching plot line leading to these creatures' home, to the start of an entire campaign, to a smaller side story hoping to save the natural land from the chaos energy of this tower.

Architecture

The entire tower is made from the primordial stuff of Limbo. In this world, that material takes on an appearance similar to that of bismuth (thus, the tower's designation). The Anarch of the Tower, known as the Talos the Keeper, can shift and change this tower as he sees fit. For purposes of adventuring within the tower, DMs are encouraged to use the random dungeon generator tables from the DMG to create this labyrinthine feeling and to connect the encounters within. The tower does not need to stay within the confines of any set dimensions. To riff off a certain British sci-fi show, the tower seems to be bigger on the inside.
The tower extends into the earth and rises ten or more stories above it. The encounters within - the creatures and places - are linked to the mission of the Githzerai. They include shadowy creatures from Limbo patrolling the lower levels and Slaadi slaves in the upper tiers. Getting anywhere in the tower is a frustrating endeavor, unless the PCs can figure out how to wretch control of the bismuth from Talos.
SOME EXAMPLE ENCOUNTERS DMs are highly encouraged to wrap in backstories or other previous encounters into these. For example, missing NPCs could appear or creatures they've faced imprisoned - to suggest the Githzerai might actually be studying them!
The Food Pens After twisting and turning through the passageways, light streams down a hall in the distance leading here. This area is an enormous room, with a series of perpendicular walkways and no floor between them. As they enter, the passageway behind them seals shut and disappears. Overhead are glaring spheres of light, providing sunlight to the inhabitants of this room. Below the level of the walkways are pens. Some contain domestic animals – pigs, chickens, goats. Others contain plants growing in ideal soil – wheat, barley, rye, rice, vegetables, and fruits. A thin layer of transparent bismuth (like mica) tops the pens and contains all sounds and smells. It may be tempting (and effective) to rest here. Nothing bothers them here all night…The five archways leading out of the food pens area are identical, and lead into randomly generated twists and turns – each with a random destination. Shadowy things haunt these halls.
The Humanoid Menagerie After some additional twists and turns out of THE FOOD PENS, an archway leads into this wider tunnel lined with six 15’ x 15’ cells. Each cell appears to have a simple archway leading into it, with no door or bars – but a transparent sheet of thin bismuth (like mica) prevents any from entering or exiting. There are six (6) cells. Each cell is labeled with a symbol from a language no one in the group knows (specifically, Gith) – these are labels that roughly correspond to the Common alphabet. Within each cell is a different humanoid or humanoids, all in a similar state – unarmed and unarmored, but clothed. Encased up to their chests in a geometric bismuth cocoon. They appear to be seated within. They each appear comatose, eyes staring blankly ahead, and their faces gaunt and aged; as if something is drawing the life from them.
The Creature Menagerie After some additional twists and turns out of THE FOOD PENS, an archway leads into a 30’ hexagonal room. Each of the five (5) walls (the entrance is on the sixth) is actually a floor-to-ceiling viewing window made of thin bismuth (like mica). Beyond each window is a terrarium-style enclosure designed to meet the living needs of a particular creature. Each enclosure runs back as far as the eye can see – this is an illusion to satisfy the animals, but in reality only runs back about 150’ in a pie-shaped wedge. Each enclosure is labeled with a symbol from a language no one in the group knows (specifically, Gith) – these are labels that roughly correspond to the Common alphabet. Nothing is obvious in any of these enclosures at first. The more insectoid creatures may venture out if they douse their lights and stay still. Standing too close to one of the mammalian enclosures will eventually lead to confrontation as the creature tests their meddle… and the strength of the viewing walls.
Careful readers will note that very few Githzerai are mentioned herein. They are cautious and know they have the PCs trapped for the time being. They bide their time before confronting them - perhaps to negotiate, perhaps to capture and imprison them - and perhaps those imprisoned experience their wildest, happiest dreams until the energy of the tower claims their bodies.

History

The tower simply appeared a few weeks ago, in response to activities of Illithid and the discovery of some campaign-specific artifacts linked to the plans of those mind flayers. Local wildlife avoids the tower and the plants nearest are dying. Even a local colony, on the verge of collapse, ended - and its inhabitants imbued with chaos energy, reanimated to create a town of the living dead.

GENERAL FEATURES OF THE BISMUTH TOWER The following facts about the environment are true unless otherwise noted in a specific area description.
Passageways. Halls are smooth and laid out in simple geometric patterns with perfect angles. They are the random colors of bismuth and average 10 feet in width and height, specifically. Passages also tend to appear and disappear, seemingly at random. It should quickly become clear that the tower is even “bigger on the inside”.
Light and sound. Beyond any light the heroes carry themselves; there is no natural lighting in the hallways or other spaces. All is dark unless otherwise noted in a specific encounter. Likewise, the halls are silent except for an almost imperceptible hum – more felt than heard.
Atmosphere. All areas contain an adequate air supply. The air is stale, but perfectly regulated to the temperature of a dry spring day – very comfortable.
Doorways. Doors do not exist, as such, in the tower. The nature of the psychically controlled bismuth (really the stuff of chaos) allows “doorways” to be created in the walls themselves, as needed, forming and reforming in a pixelated way from the cubical shapes of the bismuth. Any door they do find should be a noteworthy clue.
Travel and communication. The tower exists outside the time and space of the Prime Material plane. Communication into and out of the tower is impossible, including by any magical means known. Travel into or out of the tower is likewise impossible by magical means, including planar travel – only Gith psionics work.
Problematic spells. Any magic used within the tower works normally, with a couple of exceptions. Any spell that allows for travel within the confines of tower – e.g. misty step – is treated as if the caster was targeted with the banishment spell – reappearing on their next initiative order in their last location. Any spell that allows communication within the tower – e.g. message – includes whispers and voices in a strange tongue, unheard in any other way, but otherwise these work normally.
Healing and recovery. The chaotic power of the tower begins to take its toll on those ordered beings not accustomed to the nature of Limbo. When the heroes attempt to take a long rest, consult the chart below. All other score reductions, abilities and spells (e.g. recovering charges on items) work as normal: • First long rest – ½ HP and normal HD recovery (i.e. ½ HD recovered) • Second long rest – ½ HP and ½ HD recovery (i.e. ¼ HD recovered) • Third long rest – No HP recovered and ½ HD recovery (i.e. ¼ HD recovered) • Fourth long rest – No HP and No HD recovered • Fifth long rest – No recovery and comatose (ready for “psionic storage”)