The five Aspects have not always been so contentious.
Indeed, there was a time when they weren’t even aware of one another. Initially, their societies advanced in isolation from one another, growing in power and increasing their knowledge of their own private worlds. Arcane’s sages plumbed eldritch secrets. Chaos’s scrapwizards toyed with clockwork constructions. Tech’s corporations ushered in one industrial advancement after another.
Nearly four centuries ago, Tech mogul Katelyn Voss first discovered how to access the natural pathways through space. Ambitious and eager to capitalize on her findings, she led a hand-picked expedition to a hitherto-unknown realm of angels and demons. When the denizens there failed to bow to her authority as a prominent captain of industry, she attempted to impress them by force. Her incursion was soundly beaten back through the portal.
Undeterred, Katelyn delved deeper to see what other realms she could reach. A world of untamed natural forces. A world with legions of walking dead. A ruined world ravaged by gangs piloting machines that shouldn’t work, but did. Alas, none of her attempts to establish a foothold for her corporation succeeded. The portals simply took too long to expand, both limiting the access of her invading force and giving the defenders ample time to muster a welcoming party.
To put the odds even more against her, she was also trying to keep her efforts discrete and avoid attention from her business rivals. She wanted to keep the technique her own little secret, and for the most part she did. Rumors spread of her exploits, but few other R&D teams could recreate them, and those who did stayed similarly tight-lipped about the details. So too, in the worlds Katelyn had intruded upon, dedicated individuals tried reverse-engineering the phenomenon they’d seen her use, and some succeeded.
A decade later, all five Aspects found themselves peppered with sporadic incursions. Expansion by conquest held too much of a lure. Tech saw Nature’s forests and fields as ripe for clearcutting and strip mining. Chaos dreamed of plundering Arcane’s archives. Divine saw foreign lands as potential armies of new followers (willing or otherwise) that could help tip the scales of their own internal feuds. Behind it all, the few who mastered portaling grew rich and influential as the only people who could make these raids possible. This reinforced their desire to keep their profitable art to themselves.
Thus it went for dozens of years. In all that time, there were few major successful offenses. Though the portal-masters did experiment with different sizes and types of strike force to find the troop structures that carried through the passageway most readily, portal travel was simply too restrictive for a proper invasion force.
As time went on, the invasions were prompted more by stubbornness and pride than any potential military benefit, and the spectacle of these conflicts became their primary draw. Those who held the key to the portals went with the flow to keep their wages coming. They stoked rivalries. They adjusted match-ups. They even went out of their way to find new, unpopulated realms where opponents could clash without destroying their own lands.
Now, after three hundred years, the games are an entrenched tradition, carefully managed by the inheritors of Katelyn’s discovery so long ago.