Takkar's growing sympathy over the course of the game for the Udam, once he finds out that they're facing extinction because of the "skull-fire." It's a very harsh world they live in full of dangerous animals and competing human tribes, and yet they are being systematically killed off by something that they have no real defense against. They're just trying to survive after all, by any means they know how.
There's also the implication that said "skull-fire" is a prion disease brought on as a result of cannibalism.
The Visions of Ice and Fire represent the breadth of views primitive people might've had of nature's mysteries, depending on their relationship with it. The Udam, a tribe of literal cavemen, exist completely at nature's mercy: they are primitive to the extent that they cannot influence their environment in any meaningful way. As such, natural phenomena is incomprehensible to them. To their limited understanding, any particular natural event, whether catching a disease, the coming of winter or a bad hunt, is essentially random, at best explained by the whims of their distant gods. There's no rhyme or reason to the Udam's universe. If winter came one time and never ended, the Udam wouldn't despair because they'd think it "unnatural", they'd despair because they'd think it every bit as natural as any other possible occurrence and every bit as being beyond their control. The Vision of Ice, therefore, represents their sense of powerlessness in the face of the frightening, unknowable, whimsical universe, where a tribe might go extinct from a disease basically (from their point of view) "because the goddess decided". By contrast, the Izila are already a budding civilization. They have mastered agriculture, built permanent settlements and practice primitive astronomy. They understand, if not why, then how and when natural events are supposed to happen... Which is why a completely unexpected event, like the eclipse in the Vision of Fire, completely shatters their worldview and sends them panicking in all directions. The Wenja, meanwhile, sit in a comfortable middle ground: they know enough to understand the universe isn't random, but have not become so complacently civilized that they can't accept the possibility they don't know everything about it.
Jayma snarks about the fact that Takkar doesn't have any scars, in contrast to her. Of course he doesn't have scars: he's spent most of the game getting injured repeatedly, but the player always heals him right afterwards, fast enough not to leave any scarring.
Why is the Bloodtusk Mammoth the only Great Beast Takkar can't tame? Two possible reasons: the first is because nearly all the beasts Takkar can tame in the game are carnivores, hunting mammals, including the Snowblood Wolf, the Bloodfang Tiger and the Great Scar Bear, and the Bloodtusk Mammoth is not a carnivore, and therefore untamable. The second reason might be, given its name, bloodshot eyes, and sheer unusual savagery compared to most mammoths, the Bloodtusk might have rabies, which would render it uncontrollable.
Why would Sayla give Roshani a cowrie shell necklace to welcome him into the village, but let Dah be hauled out of his cage for a Vigilante Execution? Simple: Sayla hates Dah because he's an Udam, like the ones who killed her family. Roshani is an Izila, who have given Sayla no reason to hate them because they have not killed any of her loved ones. Also, Dah was initially a Defiant Captive when Takkar brought him to the Wenja village, screaming and growling and trying to break out of his cage, whereas Roshani is pleading and submissive, refusing to try aggravating his captors for fear of being killed. Sayla found it easier to empathize with Roshani and therefore treat him like one of her own.
The Udam are plagued by the "skull-fire" disease which they believe can be cured by eating flesh from their enemies, but its implied that doing so is what causes the "skull-fire" in the first place, which in turn means they eat more and more in an increasingly desperate attempt to cure it. Another way of describing it: they're doing the same thing over and over again and expecting things to change.
Fridge Logic
What is up with the two-horned rhino? Not only is it anachronistic but all the rhinos have two horns, just in a different configuration. It would make way more sense if the rare rhino was a one-horned Elasmotherium.
Fridge Horror
The game really nails down the terror of being a primitive caveman, barely able to comprehend all but the most immediate aspects of the world around them. Disease, natural disasters and even the weather are all malevolent, living forces which are out to get you simply because life is brutal and humans are preyed upon by them.
A Fridge Tearjerker. Imagine being an Udam and you, or someone you care about (your mother, your sister... your child) is affected by a horrific plague that eventually leads to insanity and, shortly after, a slow, agonising death. You don't understand what's happening or the cause of the plague (which only affects your tribe, not anyone else). You assume that the gods have simply abandoned you; or, worse, are punishing you for no reason. Poor guys.
The game takes place in the same universe as the rest of the series. This implies that some of the tribal superstitions about supernatural evils (the Sun Walkers are revealed to fear an entity that sounds suspiciously like the legends of demons from previous Far Cry games) are true, and that the implied supernatural evils of the other games have been around since before recorded history.
By the end of the game, the player has massacred both the Udam and Izila tribes, with any survivors lost and scattered around while the Wenja continue to hunt what remains. Sound familiar? It's exactly the same as what happened to the Wenja tribe before the game's beginning. Suddenly the Wenja tribe seems a lot less sympathetic.
How much you want to bet that somewhere out there is an Udam or Izila equivalent of Sayla, haunted by the traumatic memories of a massacre to their people which occurred for reasons they can't even begin to comprehend and wanting vengeance on Takkar? In short, it's a never-ending cycle of brutality.
There's a Blood Dragon skeleton somewhere in Oros with a cluster of eggs below it. How did it get there? How long have those eggs been incubating? And what will the Wenja do if they hatch?
