Basic Information
The Brain in a jar is a character who consists of (unsurprisingly) a brain (and often a spinal column) in some form of life support apparatus: classically a large glass jar full of liquid. Obviously - since it's a character - the brain also needs to be functioning and capable of interacting with the surrounding world. Some treatments also include a floating pair of eyes…
It may turn out to be undead (and usually floating in a jar of formaldehyde) - which is usually the best way to explain how it's still functional despite just floating in a tank of fluid1. Such a character uses powerful magic to work its will on the surrounding environment. Otherwise powerful psychic powers tend to be invoked and the life support requirements hand-waved - it operates by telepathy and telekinesis (and possibly other disciplines). The least speculative version overlaps with the wetware processor and uses the brain as a sort of cyborg (indeed a CNS-only cyborg arguably is a very specific type of brain in a jar) - the jar is only a protective float tank and the brain itself is wired into a complicated life-support system and a variety of computer interfaces with which it acts and communicates.
On the basis of ugly equals evil the brain in a jar is usually - but not always - a villain.
Sources
Game and Story Use
- Great when the BBEG turns out not to be the BBEG at all, but just the pawn of a medical curio he collected some time ago. Ideally the PCs don't find this out until the guy they sold the BBEG's personal effects to as a job lot comes down with the same villanous MO as the last guy they killed…
- The subversive non-evil brain in a jar might make for a good sage.
- In the cthulhu mythos the MiGo are known to take people's brains out and pop them into portable cylinders for study - with the correct equipment these cylinders can still interact with the world to some degree and appear almost immortal.
- Having a supposedly non-sapient wetware processor turn into one of these might be a good source of hilarity.
- Where does a brain in a jar hide? - why, amongst dozens of other (inert) brains in jars of course.
- Might be a useful variant on the lich for the role of "immortal wizard king" … if slightly less mobile and less impressive in person.
- Might go for a magical version of the CNS-only Cyborg and stick the brain jar inside a golem like body.
