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Human Scholar Brain Cylinder

Human Scholar Brain Cylinder CR 1/4

A transparent cylinder holds a single human brain connected to the inside walls with wires and tubes. The top and bottom of the cylinder have metal caps imbedded with sockets and studded with prongs for the attachment of devices. The liquid within glows eerily as sparks crawl over the brain and up and around the surface.

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; Weaknesses 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.

Section 15: Copyright Notice

Sandy Petersen’s Cthulhu Mythos, © 2017, Petersen Games; Authors: Sandy Petersen, Arthur Petersen, Ian Starcher.