The Custudo is by far the largest fighting force within the known universe, period. Within it's ranks are countless billions (even trillions) of troops fighting across many distant and remote galaxies spreading the dominance of the Empire where ever they go.
The Custudo is organized into many legions each 500,000 strong with each legion mainly having one main role (ex: Infantry, artillery, and so on) each legion is then expected to have minor branches of the other fields to have slight 'combined arms'. So every legion will have some tanks with some having mostly tanks and some infantry and so on.
The Custudo can be described as a 'sledge hammer' being used as a rather blunt force of nature used to smash enemy formations, cities, and entire worlds. While other armies are all about stealth or mobility the Custudo is about either attrition or pure force using the force of arms to drive the enemy back as well use of combined arms for all sorts of operations and support.
The main body of the custudo is of course the infantry drawn from countless worlds in either voluntary or forced nature. All soldiers are equipped with heavy armor, basic laser rifle, grenades, and MREs all of rather mass produced nature. Beyond the basic infantry are the specialists, artillery, command squads, and tank crews and gunners as well as 'Equestri' (mech troops). Beyond these are elite functions/troops that are either veterans or help bluster the ranks. Below this main body is the Auxilia split into non-citizen formations of generally light infantry or specialists the Rin need or like to use (Ex: Snipers, desert infantry, and so on)
Extra formations are also formed like the 'Suicide Legions' and 'Penal Legions' although they are deemed of lesser statues and even below the Auxilia.