Given the recent strides made by one General Sparatus, former member of the Citadel Council an in depth look at the Turian's and their Client Race the Volus is in order. Tread lightly, we'd rather not offend the people moving this sector of space forward. Admiral S.
Overview
The Turian Hierarchy is a Military Dictatorship and the Volus Protectorate a capitalistic Merchant's union, two thing's that theoretically shouldn't go together and yet they seem to balance each other out rather well for all intents and purposes. I will warn that this report will contain some racial stereotypes but at the same time such things have been historically excellent shorthand for species wide exposition. To wit end...
Biology
Turian's are a race of carnivorous Dextro Amino Protein based life-forms, meaning that if they try to eat anything with DNA in it IE most of organic foodstuff's coming out of the Union they're gonna make themselves sick, who evolved to fill the niche of an Apex predator on their own home-world. Jury's still out on how to classify them, some of the guys in the Xenobiology department are leaning insects given their hard metal like exoskeleton and mandibles, others have sighted their internal bone structure, specifically their legs, and anatomy, most notably a gizzard, and are saying birds. Me personally? I'm leaning towards 'Alien, so why are you trying to compare them to earth animals?' Turian's are stated to be poor swimmers, citing their heavy exo-skeletons, which do not make them slug proof FYI, though it does mean that they can resist the abnormally high levels of radiation on their homeworld.
Volus are a race of short, squat omnivorous aliens native to a pressurised ammonia based atmosphere, thus earning the unenviable title of Toxoids, a race whose preferred environment is completely toxic to most races, a toxic world, not to be confused with a Tomb world that being a planet that is completely incapable of sustaining life. What this means in layman's terms is that similar to what would happen should a human step into the vacuum of space unprotected in normal levels of pressure the Volus's body will experience violent decompression exploding in a shower of gore and ammonium, necessitating pressurised suits almost everywhere that they go. Aside from that? The Volus are lacking in physical power and like to avoid conflict because of that, thus they're status as a client race of the Turians.
History
As a people the Volus Protectorate is actually the one with considerably more history to them than the Turian Hierarchy, despite what their current relationship dynamics are like. The time spent on their home world Irune was marked by a extended period of corporate trade wars that usually never escalated beyond the courtroom. They were actually third to discover the Citadel, followed shortly thereafter by the Elcor, Batarian's, Quarians, Etc Etc. At the time, the Volus were hoping to be able to impress the other races with what they believed to be their superior political and technological power, but to their surprise they were beaten out in almost every category that they could think of. The Asari were better Politicians, the Salarian's and Quarians had the superior technology, the physically massive Elcor and the violent and ruthless Batarian's were the superior military might, the only category the Volus found any sort of reprieve in was in their economic prowess.
The then recent flood of alien races finding the citadel had led to the Asari and the Salarians to found the citadel council, deliberately excluding all the other races for 'not having made significant contributions to the galactic community.' This was a particularly irksome situation for the Volus who are widely credited with having created the Council's Credit backed by the use of Eezo, similar to how old cultures of earth used to back the value of money and coin with gold. Mind you given the centuries that would follow the Volus might've come out of the situation ahead of council. Case in point, the Rachni wars. The Rachni in many ways were the natural enemies to the Citadel forces, for the first time the Council had met a force that they couldn't negotiate with in the slightest, while the Salarian's and Asari's position meant that they would have to do the majority of the heavy lifting with the fighting.
The Unfortunate thing is that the Asari and Salarian's were really bad at fighting the Rachni. The insect's tomb world preference meant that they could simply camp out on uninhabitable rocks buried miles beneath the surface of the planet, the most that anyone could do was bombard their own planets whenever the Rachni took them to burn the bugs out. Fortunately for the Volus the Salarian's found Tuchanka eighty years into the conflict, and three centuries into the war with the insects the Krogan finished wiping them out. For a time the Volus entered a period of prosperity, their extremely narrow biological preferences for ammonia based atmospheres meant that there were very few planets they could claim for themselves, and none that the Krogan would want while they were continuously scooping up new worlds in an attempt to managed their insane population growth. Then the Krogan rebellions happened, and the Volus once again found themselves caught up in a conflict that they couldn't win.
We will now be speaking of the Turian Hierarchy. The Hierarchy is now and always will be a military dictatorship, a particular point of pride for them is that their entire world, Palaven, was united under a singular government before they managed to land on the moon. More recent work published by Doctor Liara T'Soni has revealed the main cause of this unification was the so-called titan war, several Reapers having been crashed into the planet in a badly wounded state following the explosive end of the last cycle, forced to shed their ship-shells in the process. Without their cybernetic shells the Reapers very much resembled giants, albeit in a variety of different configurations, and while their flesh wasn't designed to function at their size their innate biotics and psionics allowed them to manage. A combination of their immense power, huge size, and literal brainwashing abilities made it so that these 'Titans' came to be worshipped as gods, and in turn led to a planetary war for the Turian's very survival. It is believed that the Titan war was won by reverse engineering and Weaponising Reaper technology specifically their indoctrination signal which was less 'selectively kill off parts of the brain to make the subject more compliant' and more 'melt the target's brains out through their tear-ducts and destroy any electronics in the general vicinity.' Afterwards, the weapon was left behind in the tomb of the gods hooked into the Reaper's own theoretically limitless power source.
The Turian's overall growth was much slower than those experienced by the existing races of the Citadel, like the Volus they too had a narrow biological preference for worlds, similar to the Quarian's before them the Turian's required Dextro Amino Protein, or DAP, based food to live and even worse, are all consummate carnivores. Thus DAP based worlds are dedicated mainly to the growth and production of grain, which is then used to feed and maintain cattle populations, hence the Turian population is narrowed even further limiting their growth even more. The Turian's attempt at aggressive expansion pushed the limits of their colonies too far thus leading to the Unification wars.
The Turian Colonies furthest from their home-world engaged in a series of bloody conflicts with one another led by the local chieftains, the Turian Hierarchy maintained a policy of strict diplomacy with all their colonies until such a time that they had finished beating each other into submission, then swooped in and folded all the colonies back together again. Since then the Turian's maintain a policy of strictly ensuring that each colony is secure before founding another, which slowed them down even more. Even though the Turian's had started space exploration at roughly the same time as most of the other races they were the last and most recent to arrive at the Citadel proper, on the other hand while the Citadel had been embroiled in two massive conflicts the Turian's had ended several across their own territory on almost every front and so set to work on cleaning up the latest mess.
Except that, a mere decade into their entry into the war, the Salarian's introduced the bio-weapon that they had been working on to demoralise the Krogan, the Genophage. Whereas the Salarian's intended for the Genophage to be a deterrent the Turian's immediately saw the bio-weapon mass produced and mass deployed, followed by getting the council to throw everything they had at the Krogan with the intention of seeing them eliminated. It was only after the Krogan had been reduced to a handful of worlds and was once again bombed back into a pre-spaceflight civilisation that the Council forcibly held back the Turian's genocidal campaign, even then it's come to light that the Turian's planted several 'fail-safes' in place in case the Krogan would step out of line again. While these measures may look extreme, keep in mind that the Krogan had managed to render three Turian world's uninhabitable by hurling asteroids at them.
There are also reports in place that after the Krogan were bombed into submission the Turian's attempted to vassalise them, but seemingly having already learned their lesson from letting the Krogan grow unchecked the Council 'convinced' the Turian's to let them go, in exchange for a Council seat that is. At the time it was unprecedented for the Council to add new members, but at the Time the Turian's were the number one military power in Citadel space, and based on their history they would eventually be more than happy to become the number one power period after they built themselves back up. Around this time, the Volus had taken a defeatist policy, growing sick of the fact that the galaxy seemed to 'constantly' be at war, so they instead allowed themselves to become vassals under the Turian Hierarchy, under the belief that they could shape the Turian's into a tool of influence.
Culture
In their differences the two races have found an excellent partnership. The Turian's bring to the table excellent military might, discipline and training, making them the top most fighting force in Citadel space, a fact largely attributed to a strong sense of public duty which often times makes them poor entrepreneurs. The Scars of the Unification war runs long and deep, with many arguing that the Hierarchy didn't so much win as they simply kicked the already downed colonies after they had spent years fighting each other. Many colonists maintain a tradition of tattooing their faces with symbols denoting their planet of origin and loyalty, with the insult of 'barefaced' denoting someone who has no loyalty, or facial tattoos.
Turian religion believes in entities that embody a group or area called Spirits. A spirit for a Unit of soldiers embodies the honour and accomplishments of that unit, a spirit of a city or colony reflects its accomplishments and industry, a tree spirit beauty and serenity of the plant the list goes on. None of these spirits have the ability to affect the world around them, beyond those Turian's who pray to them seeking wisdom and guidance. As a rule the Turian's practice freedom of religion with some blending Asari or Hanar practices into their own, following her dramatic display at the citadel many have even started actively worshipping the Draconics own goddess Thuban. In ancient times the Turian's believed that giants roamed their planets and worshipped these Titan's as gods, but this religion has since fell into extinction following their entering the age of spaceflight, largely citing that they don't need gods to prop them up anymore. The Reality though is arguably much more impressive: The Turian's gods were very real, a group of ancient and wounded Reapers, and the Pre-FTL Turians, armed with only crude weapons and slapdash reverse engineered technology, were able to kill them.
Compare and contrast the Volus. Volus culture is dominated by their economy and trade. Land, Resources, Technology and each other have all been reportedly sold across the Volus's history, this isn't to suggest that they now or ever have approved of the slave trade, Volus have two names neither of which is a family name as it implies that the family 'owns' the Volus in question. The Volus are also aggressive traders, owners of the largest mining and manufacturing firms in Citadel Space such as Elkoss Combined Arms and Armax Arsenal as well as several banks through which they carefully monitor and regulate the citadel's currency.
The Volus are not physically adept, even in their native high pressure ammonia the Volus are short, fat and physically weak, war is thus treated as unpleasant period of time that comes about as a result of having to deal with less than pleasant races, hence their willingness to throw themselves at the feet of the Turians and become their vassals. When they do fight among each other instead of ruptured suits and explosive decompression they usually prefer ending the conflict with social death, bargains and bribes, or harsh trade sanctions.
The Volus have a sacred text known as the Book of Plenix, which describes the 'Rules of Acquisition' that set guidelines for how the Volus should conduct themselves, which aside from stringent guidelines on business and trade also advocates for charity and forgiveness in times of need such as war. The exact Quote being "Gratitude is invaluable, buy it while it's at a discount." Volus have several gods such as Cherk Sab god of luck and good fortune and Zada Ban god of punishment, the planetoid Jak Ser features prominently as the home of the gods due to it's high visibility in the Volus Night Sky.
Military
The Turian military consumes every part of their life, if there is a service in the private or public sector that can be covered by one provided by the military, they provide it. Every Turian is required to join the military for at least one tour following their legally becoming an adult at fifteen years of age, consequentially there is no adult Turian that has not gone through their version of basic training. In Turian Cities sky paths and roads are constructed to be wide enough that military vehicles can fit through smoothly and unencumbered, even with civilian vehicles parked on the side. Turian City blocks are arranged in neat organised grids to ensure maximum mobility with any obstructing structures such as trees and hills being removed to facilitate construction. Everything, cities, houses and public works buildings, only ever have one point of entry or exit to prevent them from getting flanked. The Aforementioned buildings are constructed with the intention of being able to take hits from orbital weapons up to the point of including bunkers fully stocked with food and weapons.
Turian's set themselves up defensively, there's a narrow number of dedicated DAP planets that they dedicate to the use of agriculture, and while they are perfectly capable of living on DNA based worlds they run into constant risk that something can trigger a violent allergic reaction by doing so. The Volus have similar restrictions, while they prefer an ammonium based atmosphere they make do with pressurised suits outside of their claimed Volus worlds. Thus the Turian's set up their claimed territory defensively, with heavy patrols around the entry and exit points of the planets and moons are hollowed out and turned into giant planetary fortresses to shoot at potential enemies that get close.
Ironically, in ship building, it's the Volus who are more aggressive, with the recent Kwuwu class ship being chief evidence of this. Volus Ships are built to the same size as standard Union ships, but stripped of 'unnecessary' components. Volus are only half the size of Turians, hence only needing half the space to move around. Most Volus wear their signature pressure suits constantly which acts as their own personal life support system, with the use of shackled linked VI system the average war ship only needs a crew that can be counted with both hands. Thus in lieu of these 'Unnecessary' components the Volus instead install extra weapons, extra power cores, shield generators, thicker hull plating, the list goes on. Critics and Proponents of the ship design alike have stated that the ship holds enough fire power to char a planet thrice over, hopefully it has enough to kill a reaper too.
In terms of ground forces the Turian's take priority, they are the more numerous, more durable and usually better trained, but there are some Volus who have taken to the battlefield with enthusiasm. There is a dedicated Sentinel contingent of Volus forces who go into battle wearing heavy Environmental exo armour, and who practice a unique school of biotics revolving around the manipulation of so called 'Biotic Orbs.' The orbs can be positioned to manipulate the flow of projectiles come towards them, either drawing fire away from them, or redirecting it to where their hardsuits and barriers are the thickest. They have extensive training in modifying ammunition on the fly which includes pyro, cryo, shock and warp. When the Volus really stop screwing around they encase themselves into a big metal gyroscope sphere propelled by Mass Effect Fields and armed with over a dozen gun batteries to shred enemies like cheese.
In Conclusion?
The Hierarchy is a decently powerful ally, and we can use all of those that we can get.