Role and function
The Legate system was invented by Queen Rin Sakaros to centralize large-scale military power in her own hands and provide an inherent check against treacherous ambition. Army officers were not assigned command of units larger than a cohort (10,000 beings, plus NCOs and officers), nor were Navy officers given command of anything more than a single capital ship and its escort craft on a permanent basis; when capital ships were regularly grouped together (in small groups), command of the group rotated daily among the captains of the assigned vessels.
In the event that a larger military force was necessary (usually in an offensive capacity in wartime), the Sovereign, a Royal Executor, or the Prime Legate could install any citizen to the office of Legate. Legates could be given authority over military commands of any size, though a command was usually proportionate to its task. A Legate's command could consist of forces of the Army, Navy, Starfighter Corps, or all three. Major wartime commands could even include detachments from Royal Intelligence or the Order of Keltrayu.
Legates were installed to allow the Prime Legate and the Sovereign to focus on the overall war effort while opening up multiple fronts; each "front" would consist of one or more major commands, ranging from task forces to full fleets, each under the command of a Legate.
In peacetime, Legates were sometimes created (though usually with smaller commands) to deal with potential or actual insurrection; to demonstrate a show of force while resolving intersystem conflicts; or to root out pirates, smugglers, or other criminals.
Powers and limitations
When in office, the Legate had absolute military authority over all personnel in his command, including the right of tribunal (trying and sentencing people for military crimes). While attached to a Legate's command, Royal Intelligence officers were treated as military personnel. While serving, a Legate was given a specialty pay grade, above the highest normal ranks of the various services but below the Prime Legate.
However, Legates were always created for specific purposes, and their authority dissolved when their jobs were done. If a Legate was created to put down a group of pirates, when the pirates had been eradicated, all the forces under the Legate would return to their home commands or receive new assignments, and the Legate would revert to his original military rank (if he had one). During war, Legate commands would usually last longer, but would still usually be collectively dissolved at the conclusion of hostilities.
By longstanding custom and the insistence of every Prefect of the Order of Keltrayu from Tariun Sakaros on, Centurions could not be commanded by anyone but the Sovereign, a Royal Executor, or another member of the Order. As such, only Legates who were themselves Centurions could command Centurions attached to their commands. In practice, however, the Prime Legate and Prefect often worked closely together to coordinate assignments, and each Legate's command usually had a single Centurion, designated Praetor for the campaign, who commanded all other Centurions and was expected to defer to the Legate's judgment except in extreme circumstances.
Most Legates were drawn from the active duty military. Any service member of any rank or grade could be so chosen. If substantial space combat was expected, the Legate appointed would usually be a Navy officer; if the engagement would be solely surface-based, the Legate would usually be from the Army. On occasion, two Legates were assigned, one from each service; the Navy Legate would have absolute command of space combat while his Army counterpart would control ground operations.
A Legate was given a written commission, signed by the officer issuing it, stating his exact mission and giving license to assemble the forces needed to complete the task. Every Legate's commission included a disbanding clause, dissolving his authority upon completion of the mission.
While serving, "Legate" was considered the officer's actual rank (like colonel or captain), and thus Legates were properly addressed as "Legate [Lastname]". Alternatively, they could be addressed simply as "Sir/Ma'am", and were styled "Your Honor".
Uniform and insignia
Legates who were members of the Golden Empire's military continued to wear their uniforms while serving; Order of Keltrayu Centurions installed as Legates wore their normal service uniforms. Veterans of the military recalled to active duty to serve as Legates could wear the uniform of their original service. While the law allowed the Sovereign to create any citizen as a Legate, in practice no one outside the military or the Order ever was, and so no uniform for a civilian Legate was ever designed.
Individuals with military rank continued to wear that insignia on their uniforms while serving as Legates. The only distinct badge of rank for a Legate was a gold-embroidered white stole, worn with the tails tucked through the belt. Legates were allowed to keep their stoles after their commands expired; at formal events, they could wear the stoles to honor their service, but had to wear them across the body and over the left shoulder to denote that it was no longer an active rank.
Behind the scenes
The stole is a liturgical vestment in the Roman Catholic Church, and it is from this that the different methods of wear (denoting different levels of authority) are derived: priests wear the stole in the normal method (over both shoulders, tails coming down the torso), while deacons wear it across the body.