Illithids: Hunting Tetrads
Whereas humans, for example, are often particularly fond of the numbers 3, 5, and 10, the numbers 4 and 6 (and multiples of these) occur with great frequency in illithid society.
A hunting tetrad is a unit of social organization similar to an inquisition or cult, save that while the members of an inquisition generally seek new knowledge, a hunting tetrad exists specifically to hunt down prey, or as the basic unit of an illithid military. The illithids of Gyrus claim (as they so frequently do) to have invented the modern tetrad, but aboleths tend to claim to have observed mind flayers using similar techniques concurrently across many communities.
A standard tetrad is made up of exactly four illithids, plus a highly variable number of thralls -- to be brought along as food on long journeys, or to be used in some capacity for that specific hunt. (In a military context, however, thralls are usually organized in groups of eight and sixteen.) One illithid -- either one assigned the role by the community's Elder Brain, or simply the most dominant personality in the group -- is the tetrad's putative leader. When circumstances permit, bickering and jockeying for prestige are not uncommon among members of a tetrad, though seldom will they allow such competition to get in the way of their overall goal. All members of a tetrad work together to bring down their chosen prey; this can range widely from herding them into traps, to simultaneous mind blasts, to using thralls with unusually acute hearing and sense of smell as trackers.
Rarely, one or more Elder Brains assemble a sextad -- a group of either six illithids, or a group of illithids led by one or more ulitharids. A sextad is an "elite" group formed for a specific, specialized purpose. On Gyrus, several sextads of dedicated undead-slayers are known to exist, and groups of gith-slayers are even more numerous.
The most far-ranging tetrads may travel incredibly far from home -- to the far reaches of wildspace or the planes -- either in pursuit of unusual game (read: tasty brains), rare research subjects, or individuals that the illithid deem worthy of such an expenditure of time and resources. Occasionally a tetrad of this kind will hunt a particularly reviled renegade illithid. Some track down particularly detested (and famous) individual gith, or notorious "illithid slayers" of any race. Others travel the Planes in order to capture and bring home as many unusual, "imported" brains as possible.
Both tetrads and sextads relentlessly use their thralls in pursuit of their goals. This can be as simple as using a thrall to walk over a section of corridor that may be trapped, or as complex as using dozens of thralls in telepathically coordinated assaults against an undead lair. Members of tetrads similarly will not hesitate to dominate local 'wildlife' and have them provide information or even herd their real intended prey into position.
While the members of a 'typical' tetrad usually all originate from the same illithid community, the most elite tetrads and sextads from Gyrus may actually include members of several communities whose relations are favorable, or at least neutral, toward each other. This is particularly true of undead-slaying and gith-slaying bands. The internal politics of such bands tend to be interesting as a result... The more established, long-lasting groups may essentially become political entities of their own, as if the politicking between Creeds and communities were not enough.
While many tetrad members are Tamers, it is not uncommon for other Creeds to be represented as well. The most far-ranging hunting tetrads frequently have a herd-thinner acting as a tracker and guide. Expeditions that focus on capturing large numbers of 'cattle' may have a Nourisher along with unusually potent telepathic abilities. Tetrads that focus on assassinations may include several rogues and assassins, and so on. One class that is not normally represented among tetrads from 'normal' illithid communities are mages, as arcane magic tends to be strongly frowned upon. Members of a tetrad usually wear something indicating their status. Gith-slayers, for example, generally wear gith skulls and may also wear the distinctive githyanki jewelry and even weapons.
Other methods of organization exist among the illithids of Gyrus (singletons and pairs certainly exist), but the tetrad is particularly common there and generally indicates the interest and involvement of at least one Elder Brain.
Awesome.
I'd love to see an adventure where a party has to protect a renegade illithid from a vengeance-seeking sextad of illithid hunters. It devoured the brain of someone whose information they need, and they have to take the flayer to the Crystal Palace of Shzemnar where the ancient psionicist can read the devoured sod's memories.