[[ Expanding on the eras I list on the lore page with some particulars:
On Earth, the idea of a superhero is only just now coming into vogue. Superpowers and costumed adventuring weren't unheard of in prior history, nor even the idea of supervillainy. But the idea of the superhero, and a rudimentary notion of it at best, didn't start until the 1930's.
The general consensus was that the preceding adventurers and detectives/etc. weren't as miraculous as this new wave: the proto-superheroes were mostly low-to-non-powered and largely worked within the constraints of their world and its societies or simply concentrated on matters outside of the awareness of the common folk.
Fantasy dominated this period. The mightiest superbeings of this period were majority magic-based (be it as magicians, wielding artifacts, or being tied to divinity) as had been long-standing. Even the sciences operated similarly, mostly consisting of chemists or engineers who created serums or heavy machinery augmented by unusual environmental conditions. And of course, this period was heavily populated by those mostly operating on skill and wit-- a lower barrier to access.
Early costumed adventurers and superbeings were operating independent of their local laws or home nations. The typical conventions of superheroics like secret lairs or specialized equipment occurred sparsely, along with very rare instances of robotics. Most just kept costumes and a few immediate pieces of equipment on-hand, maybe a car or a plane/autogyro if they were more affluent/connected. Some even directly wielded weapons like firearms, explosives, and blades, as well as a prevalent willingness to use them lethally.
Ties to their respective states mostly occurred in response to WWII, in defense of the homefront and public morale or for the handpicked strikeforces venturing to the major theatres of war to halt Axis Occult/Secret Weapons operations.
A brief segue between gold and silver.
With the horrifying utilization of weapons of mass destruction and the rise of international tensions between the major nations, many Golden Age heroes retired, disappeared, or were rendered outlaws by Red Scare type paranoia. Covert operations rage across the globe. A rise in attacks by local or otherworldly threats increases between human hubris and concerns from non-human cultures, primarily from space, but also from subterranea and sub-dimensions of this universe.
Few new superheroes appear and the veteran ones still active are stretched thin. Naturally occurring mutations start to spike prominently. Neo Cowboys from circuses and desert towns, in an attempt to keep alive their gunslinging skill, were sometimes also active in present day. Meteing out justice, but also performing for coin.
A more defining period of mainstays. Many of the tropes associated with superheroes (lairs/special equipment/recurring supporting casts/personal lore, and most strikingly, the dubious "no kill rule") crop up here. The advent of the atom and the space age usher in a dynasty of science, sometimes stable, other times wreaking cautionary havoc among a populace of widely emerging metaforms and visitors from the deeper cosmos invested in Earth's well-being or its subjugation. Spy agencies began to pull in special talents from among the metaforms. Not just the willing, but turning rogues and monsters in lock-up onto designated targets.
A period known for its bright optimism and bizarre situations, an overlooked aspect of the silver age was the emphasis of the superhero being loyal agent of the state: cooperative with law enforcement, operating per national interests and borders. Some of the period's greatest champions complied in order to remain active as positive forces, as well as for their own safety and those of their loved ones. Resistance was limited and scattered enough that the superhero had become the vanguard of institutional power.
The most major teams of the day were composed primarily of heavy hitters. Other groups resembled social clubs between disparate members-- those groups starting out without the acclaim of the planetary defenders, yet sowing the seeds for their eventual fortune and glory.
A past period that closely resembles the structure of the modern day. This was a time of even splits between the various potential subgenre origins that costumed adventurers could fall into. Many of the patriotically-inclined superbeings of the Silver Age continued to be active here, with a plethora of Bronze Age original newcomers offering more resistance-- a return to more grassroots efforts. Constant was the clash between ground-level problems and the newfound surge of grand scale crisis events.
In addition to the surge in newer grassroots do-gooders, major spy agencies of the mid-century would dissolve or see a consolidation of their remaining power. Former espionage/military operatives would try their hand as freelance mercenaries and security consultants, the most promising of whom were brought onto radically changed rosters of the then major supergroups,
A bridging gap between the Bronze and the Iron/Dark.
Largely takes place across the 80s. During this period, covert operations were reduced in favor of early 'guided' attempts to create high-end superbeings, the most successful of which acquired the greatest accumulation of nuclear power the world had ever seen by that point. Strides in power armor and mecha had advanced enough to create reliable models in rates that shifted the practice from hoping for a successful one-off prototype to trustworthy manufacturing and common components.
The privatization of supergroups had begun here, requiring patronage in order to acquire cutting-edge equipment and facilities. Though not beholden to loyalty oaths like government operatives, those who found themselves in A-List status would remain in order to receive various benefits and camaraderie.
By comparison, many Bronze Age newcomers, Silver Age stragglers, and Golden Age 'grandparents' were forced to form crude alliances that more resembled halfway houses-- unofficial support groups, rather than superteams proper. These outlier groups depended on each other for survival and were often marginalized within and/or without their costumed adventuring identity. But if nothing else, they continued to advocate for pressing social issues.
The privatization of costumed adventuring and the superhero took a grim turn into the 1990's. Companies that profited enough on the teams-turned-firms grew into megacorporate bodies. The decline in wide-spanning crisis events allowed these megacorps to reconsider how they filled the rosters, buying up new divisions to capitalize on genetic engineering, aging ex-military specialists and bloodlusted grungy recruits, high-tech weapons/armor production, as well as scholarships in the mystic arts. Even more than the superteams, PR and marketing teams took the reins. Not only curating their talent pool to be adored by the public, but subtly influencing the public consciousness towards their vision of history.
This period also included a fair share of increasingly strange newcomers trying to eke out an eccentric existence, simultaneously participating yet eschewing traditional costumed adventuring. For some it worked, for others it muddled. Either way, many of these weirdos would eventually settle into publicly accepted niches that would have the megacorps signing them into service, and making sure any rebellion was obfuscated and lost to time.