Worldbuilding Factions: Mercenary Guilds
Mercenary Guilds have many different possible approaches, as they often appear very differently in nature and formation in fantasy compared to their historical counterparts.
In fantasy they are more spread out across moral alignments, religious groups, and smaller populations. It's not uncommon for mercenaries to stand for their community, solving tasks and playing the same role as adventurer organizations and/or hero groups.
In the mean time realistically they served more so the roles of hirable militias, political military enforcements, and weaponized merchants historically.
I think both have great potential in writing and worldbuilding, and if explored even more can create incredibly dynamic factions that tell more and more about not just the world they exists in, but the people who work for them.
The Power of Infamy
Mercenary groups both good and bad rely on relevance, both good and bad. Most would want their actions to act as their advertising so that future clients can look to hire them. Bad publicity can help more evilly aligned guilds, as the right kind of person is likely going to hear of their infamy and look to reward them with a new job.
Although the common person may not hear of the often, powerful groups and people happen to dabble in fields where they would come across mercenary guilds that they might be happy to hire.
Take for instance a militaristic force might run into a militia for hire mercenary group in combat, after the conflicts ends they will have been advertised to all sides in a war, making good potential for the future.
For things like adventuring guilds and community mercenary groups they rely on being beloved by the places they settle in. Starting with small commissions that keep them in the people's mind, then spending possibly years to decades building up their reputation, keeps them a functional group with plenty of members and pay.
Oaths & Motives
Every mercenary group has their motives and differences.
Some might work simply on the drive to make money and output mercenaries, but have a point of denial for work where they won't go "too" far or break certain taboo.
Possibly a group doubles as another kind of faction, such as a group of paladins, clerics, hitmen, monster hunters, etc. They'll have rules from these expectations of course. They might oaths, rules that automatically get mercenaries exiled, or places they refuse to venture to.
Some mercenary guilds might be politically aligned, or even part of an extreme ideology.
They can play an incredibly dark role, such as the Oath Keepers from the United States that were present during the Jan 6 insurrection, and continue to be armed, armored, and present for a series of political protests, riots, and even armed attacks. They're not even the only militia-group of this sort, they are allied with groups like the Proud Boys and Three Percenters.
Similar groups like these can be seen all around the world for other extreme groups and political alignments.
Mercenary groups can also be merchant groups, especially historically. Take for instance the Hanseatic League, one of the most well known merchant guilds historically. They'd build villages and cities to operate, spread all across Europe. They even had plenty of ships.
Their access to German mercenary groups made them a powerful merchant organization, as they could protect and secure their goods through travel, and sabotage competition.
(There's also religious mercenary groups like the Teutonic Knights)
Guilds vs. Strays
In most instances a stray mercenary, or small group will be no where near as popular, but that on its own has some pros for people looking to hire.
For once they'll be more difficult to track down, and more discreet, with less an idea of who sent them. Someone might also take interests in sponsoring a newfound group, hiring a couple interesting characters in hopes to get things started.
However if a certain mercenary becomes something of an urban myth, heroic legend, or even celebrity they might find themselves far more active than even some of their local groups.
The main concerns on when following a group so small is that they will not have near as much resources or potentially even experience as an entire guild.
Guilds, More Like Companies
Mercenary guilds are rarely ever just "mercenary guilds". In real life they often more so operate like companies. They can also have ideologies that drive their community. Not always are mercenaries themselves even paid in money.
It's not uncommon for guilds to be joint merchant and mercenary guilds, like that of the infamous Hanseatic League. Really it wasn't and honestly still isn't for companies and corporations to this day to militaristically equipped or assisted/own (by) groups of mercenaries.
The Banana Republic. Boeing. The East India Company. Coca-Cola. Dole. United Fruit Co. Nestle... I can keep going. It gets really interesting and dark if you look into corporations versus merchant companies historically.
Power In Numbers
Mercenary groups, especially international ones, typically have power in numbers. In medieval Europe this made them particularly interesting for potential buyers, especially ones planning to hire them for use in war. Hell, even the Roman Empire made major use of mercenary. The Roman Empire's enemies also did the same thing.
In fact the larger the mercenary group also the more difficult to maintain. Who is to say that your enemies can fork up the same amount of money and purchase from the exact same company.
Mercenaries might not stay loyal or hardworking if things don't go their preferred way, they can require resources on top of payment, such as the equipment and food powered by good logistics.
But every group should know of power in numbers
Power In Range
The larger and more famous the mercenary group, the more important their range becomes. Whether they travel along merchant routes, have access to aircraft or boats, or can be shipped to the opposite end of the world in order to assists in major disasters, wars, or who knows what
When I'm worldbuilding mercenary groups that have a good range, I take in for account how they pay for travel or if they're sponsored/sponsors of particular routes. Maybe mercenaries are so common they're a people of the public, seen all the time going down the road.
------
Anyway that's all I could currently think of when I'm starting to design a mercenary guild
