Jungle Faction Lore Hopes
Way back when when Neeko came out I made a thread hypothesizing what Riot would do with the Jungle faction thinking that her reveal would be enough to solidify it as its' own thing. Obviously this didn't happen, but now with the new Jungle assassin on the horizon it seems that it finally will and our Jungle dwellers will finally get a unique identity beyond "Shurima but with less sand". To that end I took some of my old thoughts on the faction and tried to sharpen them into a unique niche for them that doesn't echo the other factions we already had. What seems to really differentiate the different regions of Runeterra is their unique outlooks on magic. Kumungus unique outlook would be to be a sort of gatekeepers of magic. They don't irrationally hate it like Demacia or use it ruthlessly like Noxus or try to harmonize with it like Ionia or worship/venerate it like The Freljord, Mt. Targon and Shurima do.
They have a very Ryze-like sensibility about it, but more extreme. It exists and it can be dangerous in the wrong hands so they try to amass as much as they can in any form to protect the world (artifacts, some Hextech and even actual World Runes). They don't trust anyone else to use it. A bit like the Brotherhood of Steel in the Fallout franchise, they respect it for what it is capable and recognize the danger, but are willing to use it themselves so long as it suits their aims.
This viewpoint came about because the Kumungu Jungle got hit pretty hard during the Rune Wars, which has had a lasting effect on their culture. The jungle is located directly south of the chunk of Valoran next to Noxus that is missing. That missing chunk is heavily suggested to be gone due to the Rune Wars, Kumungu is also located east of their desert Shuriman cousins and you don't need to look far to see the negative impact that the Ascended and Darkin had there and across Valoran. The biggest one connection is that they are situated directly west of the Shadow Isles which of course, fell victim to the Ruination not so long ago.
The reason they must keep themselves secret is because of what happened with the Blessed Isles. The isles were home to magical artifacts and healing waters that made them a target to others. Because of this Kumungu has had to make use of the untameable jungles as their ally. Their sophisticated culture and citadel is located in the center of the Jungle but the kicker is that they use dummy tribes of human and Vastaya to feign inferiority to surrounding societies (Piltover, Bilgewater and Shurima). By surrounding themselves with savages whose leaders report directly to the central command structure they can essentially maintain a completely incognito presence of the world stage. This is part of their darkness (Like Demacias' magic phobia, Noxian tyranny and Targons' misguided religious fervor) though as well. When outlying tribes get attacked, they turn a blind eye. If someone needs help they turn them away, If a tribal leader gets fed up and threatens to reveal Kumungu (or whatever Riot calls it) to the world they swiftly dispatch assassins to silence them (THIS COULD BE THE ROLE OF THE NEW AD ASSASSIN!). Anything to protect their secret. This could give off a spooky Big Brother, harmful government oversight, Edward Snowden type vibe to give the area more contrast.
The Rune Wars are a WWII/Cold War analogue, a story device that is supposed to bring that very real fear of WMDs to Runeterra. Kumungu should be that worlds' Chernobyl or Hiroshima and Nagasaki. Even in the old lore the Kumungu jungle "bears the scars of the Rune War". I'm thinking a good analogy for radiation would be magical anomalies. A little like Ionia but less harmonious natural magic and more discord, environmental damage like stuff that calls to mind polar ice caps melting and global warming and animal extinction irl. Areas of the jungle that have different gravity. Warped time. Magically enhanced Flora and Fauna. Crazy Numenera type stuff that lets us see that the magic of the runes is dangerous and can fuck the world up in the wrong hands. The people of Kumungu live this reality everyday and remember the cost of magical power and try to prevent the rest of the world from being like their home.
Just what I came up with. Came close to stepping on Ionia and the Vastayas toes but I tried my best to differentiate the faction and make it its' own.