Hi hello I have been very obsessed about your concept of territorial gods lately. How far must two (or more) gods' domains/territories overlap in order to actively cause conflict, or at least activate their territorial tendencies?
Heyo, glad to hear that you're stuck with the same brainrot that I gave myself!! The answer here is a mix of two things: personal animosity (ie, Radiance vs Unn), and niche overlap. I tend to take a very biological/ecological role to the gods of Hollow Knight because it's incredibly fun to me, but also because there is a small nugget of merit in the game itself- the major conflict is between two gods of Light, with a minor background turf war happening between Unn and the White Lady, two gods of greenery. In these cases, land = resources such as the density of worshipers, which is important because to an ascended god, receiving tribute is what sustains them and grants them their power + longevity. Essentially, worship = food, so being possessive over the source of your food is what leads to territoriality.
For the Pale King and the Radiance, both gods of Light, whose followers worshiped them as the source of said light, this means that they shared the same religious niche as each other and thus were incapable of coexisting. If a bug prays to the Light, they could mean either the Old Light or the New, so a previously-steady source of worship turned to something more capricious, even though they differ slightly (PK is the moon, Radi is the sun). Neither can or want to share. That's why PK converted the moths to worshiping him even though the territory he physically claimed was below the Radiance's and the people that he came to primarily rule over were the beetle tribe, rather than the moths- he needed to eliminate his competition by weakening her source of power. The ceding of Crystal Peak to Hallownest was something that happened incidentally, but was necessary to fully remove the Radiance from her seat of power and thus eliminate her as competition.
(That's also why I don't believe that the diminished Moth Tribe we see in-game is because of him- that would have been shooting himself in the foot. If worship is what sustains a god, then why willingly destroy your livestock? Radiance seems to have done it out of spite, but that's because the Radiance herself is a very spiteful individual, whereas the Pale King was cold and calculating.)
For Unn and the White Lady, I see it more as a primary vs secondary succession takeover, a ceding of old territory to a new, more powerful god (albeit unwillingly). Both are gods of greenery, but Unn is old and fading, and the White Lady is...well, not exactly new and spry, but she certainly doesn't seem diminished, not by anything other than her grief. They are both nature gods, but there's a slight bit more difference between their realms in that Unn is a god of moss (nonvascular plants) whereas WL is known by the Root, aka vascular plants. That's kind of why I see the White Lady encroaching onto Greenpath as a secondary succession sort of deal- in my headcanon for Hallownest, the first god was the original Shade Lord (or the Void itself, rather), and the caverns themselves were full of the Void Sea. Then, over time, the Sea slowly receded to the Abyss- helped in part by the arrival of the Radiance- and left bare rock caverns behind. Unn took advantage of this bare space to create the Mosskin and start converting the bare rock to verdant greenery via her moss (much like how mosses and lichens irl colonize and break down bare rock for minerals), and then the accumulation of sediment from her centuries as a god allowed for WL and her rooted plants to take hold and start colonizing the space in turn.
As for the Radiance and the Shade Lord- that came about partially because they are fundamental opposites, and partially because the Radiance herself is a very offense-heavy person by nature, as we see from her relentless attacks and willingness to throw hands (lasers?) in-game. Rather than squabbling over resources with another god, like she did with PK, the Void was a threat, a predator of sorts, so she had it and its followers eliminated. Crystal Peaks is as far from the Abyss as physically possible, and the moths seem to have stuck to the surface or near-surface of the caverns, but the mere prescence of the Void itself was enough to threaten her, so burned it away and slaughtered any and all who refused to either swear fealty to her, or continued to worship it. That's why there's so few traces of the Void civilization left, and why the Snail Shamans (who have a connection to void magic) are mostly hidden away, and why the place you can get the Abyss Shriek is full of their carvings + the dreamnail dialogue Our voices will cry out again. She saw a predator near her nest, and so she preemptively destroyed it. Justified, I suppose, but uh, not to that extent.)
(PK clearly didn't have the exact same reservations as the Radiance did, but then again, Soul is not the antithesis to Void the way that Essence seems to be- probably bc of the moon metaphor going on with him vs the Sun vs the Night one that Radi and the vessels have. He can work with the Void, even if its dangerous to him. Though I shall also make the case for him having a scientific curiosity for it which affected how he interacted with it.)
All of these reasons are also why PK and WL can coexist peacefully too- PK is a God of Light and Mind, WL is a God of Root and Life. Their aspects and realms of worship don't conflict with each other- they coexist. So a mutualistic relationship is not only possible, it's beneficial, and that indeed seems to be why they thrived so well pre-fall. It's also why Hallownest (as in, the Hallownest that the Beetle Tribe claimed) was also so big- because those were the territories of two gods merged and working in tandem, rather than guard what they had alone. It's also why other Higher Beings could exist next to PK with relatively little conflict, since he had no interest in their worshipers and they wanted nothing to do with his- though WL ofc had some contesting with Unn.
I will say that in my hcs as well, unascended wyrms are the exception to all of this- they are incredibly territorial because their massive ever-growing bodies are nutrient sinks on both the mortal and spiritual plane. That's why they're incredibly violent interritory altercations, despite the rule of thumb for pretty much all living things being a conflict-avoidance policy if possible: territory wars and/or mating events can also double as a massive food source if they can kill the other god, so fights often rapidly escalate to the death with them because if they can't win a territory, then hey, might as well raid the coop while at it. This isn't something of 100% certainty because if a fight turns bad for them then they WILL disengage to conserve energy (and they usually do their damned best to avoid other wyrms in general), but that isn't something you want to risk. I hc that PK arriving to Hallownest raised a whole bunch of alarm bells in the residant gods up until he killed himself to be reborn anew, which was such an un-wyrmly move that it settled everyone's hackles back down again (bar for Radi, but she never would have been able to coexist with him anyways). And then PK giving up his wyrm form meant that he didn't need to eat practically at all on top of the energy gains he got from worship, so that saved everyone a lot of trouble too.
