The lands were city states, then consolidated under warlords, who became kings once their dominions were well-established under cease fire in their descendants’ days. At that time, the strongest were directly the rulers, and their advisors. Over thousands of years, however, with kingdoms rising and falling, collections of mercenaries daring to delve into ancient ruins, attain levels of skill that sedate rulers lost, and gathering reservoirs of old magics at their disposal, exceeded the power of standing armies. As this became more and more underscored, with proxy wars fought by adventurers for kingdoms, standing armies and fortifications became moderately obsolete. Power became the ability to hire the best adventurers.
Nobility ceased to be meaningful, in favor of two sorts of skills former the upper class: financial acumen, and excess combat prowess.
Guilds which have obtained monopoly within their area either seek expansion, or divide from disagreements within. Weaker guilds merge for common strength, or compete for territory. Success as an adventurer’s guild means money, means power. And merchants aren’t willing to use non-guild mercenaries, even though cheaper, for fear of the adventurer’s guilds blacklisting them.
Standing armies don’t really exist anymore. At best, each town has a somewhat trained militia; and for all greater threats, adventurers are called upon.
There are 17 Adventurer’s Guilds, spread out over 7 nations. Each has sufficient consolidated power to act as their own paramilitary task force, which have made standard military forces partially obsolete. Through strict regulation of legality of magic item manufacture, price, and ownership, its become nearly impossible for non-guild adventurers or normal soldiers, even highly skilled veterans, to compete with the guild’s power. Each guild tends to be run by its founding or strongest members, often retired from adventuring to administrating. Governments tend to be formed of merchants, whose profits from trade fund the mercenary Adventurer guilds, to protect their assets, spy on competitors, and ensure war does not arise and threaten business.