An electoo is a sophisticated subcutaneous tattoo that utilises crystalline circuit technology to allow its user to store or manipulate digital information as part of their own body. Variants of Imperial electoo technology, such as that used by the Electro-priests of the Adeptus Mechanicus, can even allow a user to unleash and control vast amounts of electromagnetic energy.
An inert layer of conductive material is inserted beneath the skin to create the foundation of an electoo. Sometimes this layer is injected and allowed time to form before the process can continue. Crystal circuitry stacks are built up on top of this film and the waste material is simply allowed to dissolve out of the body. The electoo can then be programmed to function as any form of digital control or monitoring device.
On Terra everyone carries an electoo containing personal details, their credit ratings, security grades and access, and details of their social record -- together this information acts as a police file and automatic credit facility. Sensors at building entrances read the details of every electoo-carrying individual that passes through them, so a constant record can be built-up of every individual's movements. Similarly, when an individual purchases anything, a till-sensor automatically modifies the credit rating of the electoo accordingly. The system is also used throughout the Adeptus Terra and on some Imperial worlds either generally or within specific social levels. As electoos are invisible they are ideal for carrying secret messages -- information is coded so as to be almost useless except to the intended recipient. An individual with an electoo need not even be aware of the fact, and certainly wouldn't be aware of its contents. Electoos carrying secret messages can be split between several people and only work when the information encoded into each is joined.
- Electrografts - Electrografts are a special form of electoo engineered directly onto the recipient's cerebellum. This involves cutting away a portion of the skull and creating the electoo directly on the brain tissue before (usually) replacing the section of cranium or covering with synthetic material. An electrograft reacts with the brain to alter a creature's memory, personality and knowledge. Many of the Imperium's technological secrets are passed on by this means, and it is certainly a quick and easy way to learn how to speak new languages, operate machinery, etc. On the other hand, interference with the mind tends to cause personality disorders, problems with memory recall and occasionally total mental breakdown. Once inserted an electrograft can be reprogrammed almost indefinitely, although repeated re-use accelerates the degenerative process.
- Skinplants - Skinplants are sophisticated tattoos -- very sophisticated. The miniaturisation possible using crystalline circuit technology makes it possible to create a functioning device between layers of skin. The device cannon include mechanical components or utilise large amounts of power. The most popular application of this idea is to power and control an electrically-sensitive tattoo. Any Imperial citizen with sufficient credit can have a device or logo implanted on their forehead which actually lights up and flashes. This can either be controllable, light-sensitive, or a permanent fixture. The subcutaneous wristwatch is a standard way of keeping the time -- light pressure on the wrist activates the digital display beneath the skin created by the skinplant. An individual could even go to the lengths of having an entire limb or his whole body glow if he or she chose to do so. A light-emitting patch on the palm will illuminate a small area within 10 centimetres and is popularly known as the "thief's light," providing sufficient light to pick locks, operate switches, etc.
Every one of the Omnissiah's worshippers is fitted with a personal electoo. Taking the form of subcutaneous circuitry, some of these devices are little more than small identifier-plates and information wafers that can only be accessed when illuminated by senior Tech-priests, much like the simpler forms found on Terra. Others are far more advanced. The electoo networks the brotherhoods of the Electro-priests implant beneath their skin are so extensive they cover the entire nervous system, their bio-electric pulses potent enough to send out bursts of scorching power known as a "voltagheist" field that intercept incoming projectiles. Through devices such as these, the manna of the Machine God can visit Fabricator-General and lowly Skitarii warrior alike. Even Servitors and robots are blessed with their own form of electoo, as much to brand them as the property of their masters as for the religious rapture they can bring.
Through these electoos, the disciples of the Adeptus Mechanicus can channel the electric majesty of the Omnissiah. So are the faithful bounteously rewarded, as they are filled with a glorious ambrosia of data, their floodstreams thrilling with each new pulse of the sweet nectar of pure information. In times of battle, an entire procession can have their electoos remotely set to respond to the same canticles and invocations. In doing so, the leaders of the Cult Mechanicus ensure that every member of their cybernetic congregation is simultaneously filled with the divine ability to destroy its foes in spectacular fashion -- be it with blasts of living lightning, piston-driven fists, or the blinding light of the Omnissiah's truth.
- Codex: Adeptus Mechanicus (8th Edition), pg. 44
- Codex: Adeptus Mechanicus - Cult Mechanicus (7th Edition) (Digital Edition), "Fulgurite Electro-Priests," "Corpuscarii Electro-Priests"
- Warhammer 40,000: Rogue Trader (1st Edition), pg. 270
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