Brain Cylinder

Human Scholar Brain Cylinder (CR 1/4)

XP 100
Human brain cylinder expert 4
LN Tiny construct
Init –5; Senses Perception +8


AC 5, touch 5, flat-footed 5 (–5 Dex, –2 object, +2 size)
hp 21 (4d8)
Fort +1, Ref –4, Will +5
Defensive Abilities half damage from sonic, fire, and ranged attacks, hardness 10; Immune cold, construct traits, critical hits, nonlethal damage
Weakness immobile


Speed 0 ft.


Str —, Dex 0, Con —, Int 15, Wis 8, Cha 10
Base Atk +3, CMB +1; CMD 6 (can’t be tripped)
Feats Alertness, Iron Will
Skills Appraise +9, Diplomacy +7, Knowledge (arcana) +9, Knowledge (geography) +9, Knowledge (history) +9, Knowledge (local) +9, Knowledge (nature) +9, Knowledge (religion) +9, Perception +8, Sense Motive +8
Languages Aklo, Common, Sylvan


Environment any
Organization solitary, pair, or collection (3–20)
Treasure none

Brain cylinders are alien technology, originating with the fungi from Yuggoth. They are used to preserve intact the brains of other organisms so that the fungi can carry them into space or other worlds. The fluid within the cylinder has a faint glow, and particles of light can be seen “crawling” up and down the brain and brainstem. Unless the brain is of unusual size, the cylinder containing it is not particularly large—only a foot or two long at most and half as wide.

Cylinders need not be transparent and can be made out of any substance, including metals or other materials that are typically used in forging armor. The fungi themselves tend to make the main part of the cylinder out of armored glass, which is difficult but not impossible to pierce.

Brain cylinders never run out of energy–they can keep a brain alive and well for centuries. The extradimensional fluid taps into other planes of existence for its power.

Cylinder Attachments

The cylinder has a number of plugs for attaching devices to it, which enable the brain to see, hear, and communicate, as well as perform other functions. The fungi have a huge variety of devices they have created for the cylinders, including means of interrogation and even torture.

The devices that plug into the cylinder can easily be modified from magic items built for humanoid races, and the cylinder itself is made from normal terrestrial substances. Cylinders can even be constructed by skilled human craftsmen. The true alien technology is not the cylinder itself but the liquid in which the brain floats. This substance is partially extra-dimensional, as are the fungi themselves and has a sort of life of its own. The transparent fluid constantly repairs and maintains the healthy state of the brain, preventing deterioration. It even cures existing ailments, averts new ones, and effectively grants the brain immortality.

The fungi are able to plug brain cylinders into biomechanical constructs and use them to control work machines or other large and complex devices. These constructs are rare outside of the fungi homeworlds since they are heavy and often quite large, making them difficult to transport.

Control Drones

A control drone is a bio-chemical-mechanical creation. It is partly surgical in nature, mostly organic, and partly cybernetic. Drones come in a variety of forms, but typically stand well over 10 feet high. For the sake of accessibility, the controlling brain cylinder is visible in a clear organic dome on the drone’s top or front. These drones are mostly fungus with some crab- or spiderlike parts. The brain cylinder can speak mechanically through attached loudspeakers.

While most such drones are simply work machines, they can be adapted for combat, typically through the installation of grasping limbs or tentacles. The drones are remarkably resistant to damage. Their main vulnerability is the brain cylinder itself: if the cylinder is destroyed, damaged, or simply removed from its socket, the drone becomes inactive. This is intentional on the fungi’s part, as a means of discouraging a slave rebellion.

Usually the drones are only found on fungi bases where they work in heavy construction. A rare few drones are huge, sometimes hundreds of feet tall. On these more potentially dangerous devices, the brain cylinders are always placed on the very top, while typically the drones’ grasping limbs are placed so that they cannot protect the cylinder from above. Thus, in case of a massive drone going rogue, a mi-go can simply fly down from above and remove the cylinder, immobilizing the drone and preserving such a useful platform from further damage.

Control Drones in Combat

Control drones come in a dizzying variety of shapes, but many are functionally similar to a flesh golem, minus the golem’s immunity to magic and with the attached brain cylinder's mental ability scores and faculties (as if the brain were possessing the flesh golem with magic jar). The constructs are designed such that they cannot manage the fine motor control necessary to provide somatic components for spells. A brain cylinder has a CR of 6, unless it has extensive magical abilities it can use without somatic components, which is exceedingly rare.

Attacking the brain cylinder is a sunder combat maneuver and applies damage normally to the brain cylinder itself. An attacker familiar with mi-go mechanisms can also detach the brain cylinder with a grapple combat maneuver. In either case, the drone gains a +4 bonus to its CMD against such attacks from below or from creatures smaller than it but a –4 penalty to its CMD against these attacks from above or from larger creatures.

Creating a Brain Cylinder

“Brain Cylinder” is an acquired template that can be added to any corporeal living creature that has a brain (referred to hereafter as the base creature).

Challenge Rating: A brain cylinder has limited methods of interacting with the environment and typically has no way to attack or defend itself physically, giving it a CR of 1/4. If a brain cylinder retains spell-like abilities, psychic magic, or other significant methods of attacking and defending itself, its CR is equal to that of the base creature –1.

Type: The creature’s type changes to construct.

Size: The creature’s size is reduced by three size categories (minimum size Diminutive).

Senses: A brain cylinder is blind and deaf unless it has active attachments that grant it vision and hearing. Typically, these attachments only grant vision and hearing equivalent to those of a human, so it loses lowlight vision or darkvision. A brain cylinder loses all other senses that depended upon a physical body.

AC: A brain cylinder loses all natural armor bonuses possessed by the base creature, but gains a +6 armor bonus from its armored glass casing.

Hit Dice: A brain cylinder drops all racial HD but one and changes that one racial HD to a d8. Creatures with class levels retain their HD. As a construct, a brain cylinder does not have a Constitution score and does not gain bonus hp from this ability, but it does gain bonus hp according to its size if it’s large enough. (Most brain cylinders are Tiny and gain no bonus hp from size as a result.)

Saves: A brain cylinder with class levels retains its saving throw modifiers from its class levels. A brain cylinder without class levels has base saves of +0 for all three saving throws as a result of its one racial HD as a construct.

Defensive Abilities: A brain cylinder gains hardness 20 from its armored glass casing. It is immune to cold damage and takes half damage from fire and sonic damage. Any energy damage (except electricity damage) inflicted on a brain cylinder is halved before applying its hardness to determine actual damage. Ranged weapon damage is halved as well, and brain cylinders are immune to nonlethal damage and critical hits.

Weakness: A brain cylinder is immobile and is treated as an object. In addition to having a Dexterity of 0 (and thus gaining a –5 penalty to AC), a brain cylinder has an additional –2 penalty to its AC. Furthermore, a creature can take a full-round action to line up an attack against a brain cylinder to automatically hit with a melee weapon or gain a +5 bonus on attack rolls with a ranged weapon.

Speed: A brain cylinder is immobile. It loses all the base creature’s speeds.

Attacks: A brain cylinder has no method of attacking. It loses all the base creature’s natural attacks.

Special Attacks: A brain cylinder loses all special attacks that rely on the base creature’s physical body. It retains all spell-like abilities possessed by the base creature, as well as all purely mental abilities. If the base creature was capable of casting spells, it retains that ability but cannot cast spells with somatic, material, or focus components. It can only cast spells with verbal components if it has a speech module attached (see Languages, below), and cannot target spells if it has no vision module attached. Without a hearing module, a brain cylinder is deaf and suffers a 20% spell-failure chance. Spell-like abilities function normally when used by a brain cylinder, as they are activated mentally.

Likewise, psychic magic functions normally for a brain cylinder, although the traumatizing distraction of being a detached brain makes emotion components difficult. When casting a psychic magic spell with an emotion component, a brain cylinder must make a concentration check (DC = 15 + spell level) in order to cast the spell successfully.

BAB: A brain cylinder has a base attack bonus of +1 but cannot make attacks on its own. If the base creature had class levels and thus retained its Hit Dice, the brain cylinder’s base attack bonus is the same as that of the base creature.

Abilities: A brain cylinder is treated in many ways as an object as well as a construct. It has no Strength or Constitution score, and its Dexterity is reduced to 0 (thus giving it a –5 penalty on all Dexterity-based checks). The trauma of being transplanted from a body to a cylinder results in a –2 penalty to the base creature’s Wisdom.

Feats: A brain cylinder loses all feats gained as a result of racial Hit Dice save for one feat of its choice. A brain cylinder retains all feats gained as a result of class levels and associated Hit Dice. Note that some feats become useless for a brain cylinder if it no longer qualifies for them.

Skills: A brain cylinder treats all skills as class skills. It retains all skill ranks gained from class levels. The brain cylinder loses all skill ranks gained from its racial Hit Dice, but gains skill points equal to 2 + its Int modifier (minimum 1) if it gained 1 racial Hit Die as a result of applying this template. Although a brain cylinder loses the base creature’s skill ranks, it retains the knowledge it had as that creature and gains an insight bonus to the base creature’s skills equal to the base creature’s skill ranks in that skill.

Languages: A brain cylinder retains all the base creature’s languages, but cannot hear or speak unless the proper attachments are affixed to the cylinder. Attaching or detaching one of these devices to a brain cylinder is a standard action.

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