Horizon Zero Dawn
Horizon: Zero Dawn is an action RPG produced by Guerilla Games, who thought one day, "What if we made a game about a cavewoman fighting mecha-dinosaurs?" Then they made a very pretty setting and a book's worth of lore to justify it, but here's all you need to know: there is a metal panther with buzzsaws for a mouth running around crushing houses. Go stab it with your spear.
No, seriously, what is the plot?
You play as Aloy, an orphaned barbarian who's obsessed with finding her mother, for some reason. As a baby, she was found alone in the sacred cavern of the Nora, a tribe of matriarchal hunter/gatherers who like to shoot foreigners. Some of the Nora felt intimidated by the baby and wanted to kill her (the Nora are dumb), others thought she was a gift from their Goddess.
Guess who ended up being right.
Anyway, they compromised by asking another outcast (a guy named Rost) to adopt her, and then gave them the silent treatment for 18 years, because everyone knows ignoring problems makes them go away. Luckily, Rost was a badass "machine hunter"- someone who survives by hunting the animalistic robots that populate the setting and stripping out their armor to use it as currency. He passed on his skill to Aloy, partly because Horizon's Earth is very dangerous, and partly because she wouldn't stop whining about it.
While all this was happening, humanity encountered a problem. The machines, once docile and no larger than your average deer, were inexplicably becoming territorial monsters who killed people on sight. New machines- built solely for combat- started to show up. Worst of all, none of the tribes populating Earth (whose knowledge of tech peaks at "waterwheel level") had any idea why this was happening or how to reverse it. This change was called "the Derangement".
The Nora, as always, chose to hide away in their alpine "Sacred Lands", which doctrine forbids them from leaving on pain of eternal exile. (Rost was outcast because he left the Lands to kill his family's murderers.) Given that the previous Carja king, a slave-taking Aztec sadist, was only deposed a few years ago, this approach was not without reason. However, it came to nothing when all of their new warriors ("Braves" for that American Indian flavor) are ambushed during the Nora's annual rite of passage. Everyone got massacred, except Aloy, who was participating in "the Proving" for her own reasons (the Nora being the only people who might know who her mom was, and placing first in the Proving being the only way she could force them to tell her). As Aloy's recovering from her injuries, one of the few non-asshole Nora shows her the cavern where she was found and tells her the truth: they don't know who her mother was. Luckily, Aloy recognizes the Old Ones (pre-apocalypse humanity) tech filling the cave. She decides to leave the Sacred Lands and search other Old One ruins, in the hope that they might hold a clue. Oh, yeah, and bring the braves' killers to justice. If she has the time. (It is an entirely optional sidequest.)
Carja?
The setting is populated by several tribes, who hold all the typical distrust and racism towards each other that will be swept under the rug so the finale can have a cool "everyone allies" scene. The Carja are one of these "tribes", although politically they are a kingdom centered around a relatively advanced city. In more detail:
Carja
Desert/jungle folk ruled by the supposedly divine Sun-King. They mostly live in Meridian, the setting's only city, and have a lot of religious and aristocratic drama (not human sacrifices anymore though, they stopped doing that). They are patriarchal sun-worshippers- the exact opposite of the Nora- and the only race who aren't some flavor of barbarian. This makes them a bit stuck-up, but mostly the Carja are good people. A few years ago, the Carja were ruled by a crazy Sun-King named Jiran. He instituted public blood sports, claiming they would stop the Derangement, and the murderous Red Raids against every other tribe. He was no nicer to his own people, condemning any who dissented to death in a gladiator ring and executing his own son for speaking out. Luckily, the second son in line managed to escape Meridian, eventually usurping Jiran with the help of sane Carja and the Vanguard, a band of Oseram mercenaries. Now, Sun-King Avad strives to reconcile the other tribes with his people, eradicate remaining Jiran loyalists (they fled to a shithole named Sunfall) and institute a lot of left-wing policies; letting foreigners have high-level jobs, permitting women to fight, being nice to everybody, blah blah blah. You know the drill. For the most part, this has worked, and the Sundom (as it is known) is a beacon of peace and inter-tribe trade.
Oseram
The setting's blacksmiths. Most Oseram come (flee) from the Claim, a place with a lot of arguing about everything and beliefs about what women can't do. The Oseram are comfortable with tech, unlike all other tribes, and even build their own. They tend to wander through territories, trading stuff as they go. A lot of diplomatic work is outsourced to Oseram people, because every tribe knows them. Personality-wise, most Oseram are crude, bluntly honest, and practical. Think dwarves, if dwarves were human-sized and a bit trigger-happy with their cannons.
Banuk
Tundra barbarians who live in nomadic groups known as "werak". They know how to pacify machines by imitating their sounds, and unlike all the tribes live alongside machines, which they revere as spirits of the natural world. They still kill them for parts, of course, but mostly Banuk have escaped the superstitious fear of the Old Ones that cripples everyone else. Culturally, the Banuk are very artistic (in the areas of cliff painting and music) and spiritual. Weraks are led by a typical tribal chieftain and the group's best shaman, who uses the "Blue Light" (a metaphor for life itself) to command machines. Banuk are very socially-Darwinist: if you can't survive the ice, it's your fault and no one should respect you. Even their leadership is based around proving who's the toughest, regardless of ethnicity or leadership ability (this has bitten them in the ass several times). They choose to live in arctic regions because they think hypothermia makes them stronger. For some reason, the Banuk also have better bows and armor than anyone else. Not because it makes sense in lore, but because the game's only DLC pack revolved around them, and offering gamers powerful loot is the best way of making them buy stuff.