Set post-0 AF, pre-400 AF, spoilers. Caius has had years to fall from faith - and Etro's actions have not helped him resolve the paradox between divine omnipotence and failure.
It should be heresy to think that one's goddess is an idiot.
If it were heresy enough, Etro should have struck him down by now. Maybe it's only more proof of her bumbling benevolence that she doesn't.
But Caius can't avoid the conclusions. Etro saved him from death by caging him in immortality. Etro saved Cocoon from Ragnarok by turning the Pulse l'Cie into crystals, only to have Cocoon spurred to greater extremes in the aftermath. Etro saved l'Cie from a frozen fate by undoing their sleep and removing their brands - and in doing so, invited chaos into the world on a grand scale, bleeding out her remaining strength to drag it back to Valhalla. Every step of the way, Etro fashioned her own destruction, and if that isn't an overly complex machination for suicide, then Caius can only interpret it as utter short-sightedness.
Either his goddess - the entity whose heart he carries in his body, whom he believed in once above all others - is a schemer fit to triumph over every power in history, or is horrendously incompetent.
There are days when Caius wavers between the two. His thoughts roll around and around, like ageless chocobos in a fixed racetrack, unable to stop or escape. Etro doesn't answer when he rages. She doesn't answer when he pleads, and by now, Caius is so accustomed to the goddess's silence that he rambles to her out loud at times, not caring if he looks insane, or devout. Perhaps both.
Sometimes it feels as if Caius has two modes for himself: sleepy and homicidal. One restricts the other. He's forged his own chains from patience, the patience of a human who's forcing himself to remain passive, because if Caius allows himself to think, he'll be overcome by fury. Instead, he keeps his thoughts quiet. He hammers them down until they splinter, like tiny shards of glass twinkling in spade-turned loam, shredding errant hands that search for roots. He crushes his emotions into dormancy, laying a bed of cool soil over the volcano beneath - and he flies whenever it threatens to erupt, shifting and falling and soaring, changing forms effortlessly as he allows Bahamut to possess his body and reshape his bones to rage.
His is the most laconic apocalypse ever, because if Caius lets his self-control slip, he may never stop screaming.
Immortality would be a long time indeed, if he were ever to go mad.
It is winter over the Archylte Steppe, and the grasses are yellowed and tough, dry as the hair of an old mother. The adamantortoises are congregating in sluggish herds, nudging one another and lowing in deep, baritone croons. Cocoon's frozen pillar overshadows the sky. Clouds sulk along the horizon, smearing their outlines like white mud.
It is winter, and Yeul has spoken longingly of the summer sun, in the regretful tones of one who does not expect to see it again.
Caius hunts for them both, using the oldest of methods, and the least intrusive. Loops of twine and sinew get buried among the steppe's thorny brambles, where they wait for careless foragers. His snares are meant to kill; they do not imprison. Merciless, they snap the necks of small rabbits like children, faster than any gasp.
Luck does not always smile in Caius's direction. He catches inedible creatures as frequently as palatable; his lures are stolen, his kills are snatched, but Gran Pulse is a hungry land, and he expects as much when he sets out his traps. When necessary, Caius is able to fast for days, if it means that Yeul is fed. The gnawing in his belly is nothing, a mere series of pangs, like raindrops flicked against a bucket. Like rain, they will pass. He has gone without sustenance many times in the past when the tribe has been light on supplies, and if it comes to it - if he must - he can always let Bahamut out to sate his appetite.
But for now, Caius hunts in human ways, keeping to human hands and human sensibilities for picking his meals. He dodges around a pack of goblins - too gristly, and this Yeul declines meat as much as possible, which has forced Caius to become particularly creative regarding her nutrition - and ignores when they flash offensive gestures in his direction.
He turns away from their posturing, their harmless, petty scorn, and casts his gaze across the fields.
A cluster of gorgonopsids lopes by, heads lowered and jaws dripping with long strings of drool; they move with the sleek unification of a pack that has fixed upon its prey. Atypically for winter, the beasts have the luxury of sport, for their target is a slow-moving navidon, too cumbersome to flee. Some accident has damaged its shell permanently, caving in the left side from shoulder to flank; slivers of its carapace hang off in snapped spokes. The gap is a prolonged death sentence. If the gorgonopsids do not finish the navidon off, any number of other predators will.
Caius would be lying if he said he was not one of them.
Knowing the pungent taste of armadillon meat from experience, he studies the developing confrontation with tepid interest. It might be worth leaping in to claim the kill. Or to target the gorgonopsids, possibly - he could pick off a few of the beasts and flay them for the spit. He deliberates while the gorgonopsids growl and snap; the navidon scrambles backs against the cliff, instinctively hoping for a protection that will only manifest as a trap.
Inexplicably, Caius lingers, even after dismissing the navidon's fate. Something here will die - of that, there is no doubt. He knows this. He knows. There is nothing remarkable about it that should draw his attention.
The brooding in the back of his mind solidifies again into a single point. Etro.
Only she could change the odds for survival. Only she would. It would not be impossible for the navidon to be saved at the last minute by an act of bizarre, divine grace. The skies might wrench open at any second, raining down lighting to scorch the attackers. Etro might split the cliff face into an escape route, might erase the entire species of gorgonopsids from history, might slaughter five tribes to protect the newest jewel to catch her eye.
Caius scowls down at the stunted grasses. Against his own will, he waits.
Like toothy river-minnows, the gorgonopsids press up against the navidon's defenses; they twist and snap at the carapace, testing again and again until one of them finally slips through the broken slats. A terrified screech splits the air; the navidon's blood sprays across the grass. As the beast attempts to turn its hips into a tail lash, another gorgonopsid ducks neatly under the rippling shell, and goes for the creature's throat.
Etro did not save the prey this time.
Paired bursts of disappointment and resignation flare in Caius's chest. He should have known that the goddess would not care about a single paltry monster - and yet, it would not have surprised him either if she had. Nothing about her could surprise him any more. Etro was so careless in her consequences that logic seemed to have abandoned her long ago. Each generous gesture had merely spun the chaos wider, distorting timelines like ripples on a lake. If Etro were the only one to suffer, her actions might have been passable - but Yeul's lives were offered up to pay the fines of the goddess's whim, sacrificed over and over because Etro happened to fancy a few paltry humans.
If Caius were a god, he would have done better. If Caius were to make the world -
Bahamut rumbles inside him, and then breaks free with a snap of its wings, tearing through Caius's self-control and skin like layers of damp gauze. Chaos remakes flesh. Caius rolls under the sensation, his spine twisting and writhing as it elongates into a new shape; the tail splits through his bones and thrashes in a serpent's fury against his ankles before it stabs at the sky.
He does not allow the Eidolon free rein entirely, regaining control again even as the metamorphosis culminates. His massive weight sways back and forth, claws digging into the sod, raking open wounds on the earth. With a snap, his tail catches in a bush and whips free, shedding twigs as it coils underneath his legs. The air in his lungs puffs, snorts, and then calms.
Bahamut is a part of him, though it answers many callers. The more powerful Eidolons can manifest for more than one summons, even simultaneously, casting reflections of themselves into a hall of endless human mirrors. Very few l'Cie offer up their own bodies for fuel. Very few can - and Caius is the only one who can Incarnate more than once, because it doesn't succeed in killing him each time.
It tries, though. It tries hard.
He knows there was a time before Bahamut. The Eidolon, in turn, knows there was a time before him. But when they are merged together, the power smothers everything into an eternal wave of present; it reduces and compresses time like a melting candle, erasing the concept into a streak of mere color. Each day, Bahamut prowls beneath Caius's skin; it boils and hums within the sword, resenting whenever it is bound in a form that is not Caius's own.
Even this, even this is another shortsightedness of a goddess who has no excuse not to witness the timelines, for Caius will use the very Eidolon she gifted him with to help destroy her.
Etro must know. She must have known it from the start. She must either desire Caius to kill her, or be a fool.
Frustration bubbles up again. The Eidolon roars in his blood. Caius quiets them both, automatically; then he gives up, surrendering to bleak inevitability, and lifts his cruelly-muscled arms to the sky.
The gorgonopsids scatter like sand when he tears into them. Startled by the new predator, they bay with bloody jaws; one springs forth uselessly to fight for the navidon's carcass, and Caius opens its belly with a flick of his claws.
The downbeat of his wings breaks bone. He picks the gorgonopsids off when they attempt to flee, scooping them up like squirming fruits, only to fling them against the stones. His strength wrenches limbs out of sockets, crippling the gorgonopsids into a pain-crazed frenzy as they attempt to drag themselves across the ground on their bellies. He ignores each of their desperate shrieks as he rends their bodies into the smallest parts, and Bahamut howls with rage enough for all of them.
The sun is low in the sky. Caius licks blood off his fingers, absently rubbing his thumb against his teeth. A gobbet of tissue had dried along the nail. He worries at it until it breaks free, and then swallows.
It doesn't taste as good as when he's Bahamut.
His clothing is a mess. He's already delayed in returning to Yeul - the sun has leaked nearly all of its radiance, slipping closer to the horizon - but Caius is wiser than to return to her with mayhem stained across his body. Yeul is no innocent, of course. She knows his capacity for violence; she knows him, in all his ability and cunning, all his smothered emotions and self-discipline.
She must know what he intends in the future. She must. Like Etro must know, and agree with, because Caius has not been cast aside by either of them yet. It must be intended.
He cleans himself at the nearest river, reeling patience back into place. The pace of his breathing is steady. In 700 AF, the world will end by default, humanity died out at last. Despite that, Caius knows the prophecies: his best chance of baiting the threads lies in 500 AF, though one of the people he'll be counting on won't be born for close to two centuries past that.
He wonders how that will feel, to live two hundred years past the time when someone else is meant to kill him, if he'll remember death in advance or simply dream of it. He knows it will be a boy called Noel, because Noel will be the only human left by that time. And if - if only Caius lets that go, kills everyone he can reach now and allows no other human to be born, then even the Farseer tribe would come to a close. Their termination would simply arrive early. 700 AF is too long to wait.
Yeul would not be reborn. Could not be, not without humans. Should not be.
But her soul might be trapped in other ways, imprisoned in Valhalla in agony for not being able to return. Or Etro might yet devise some other torment, disguised as kindness; Yeul might be forced to reincarnate in a beast, in the past in a never-ending loop, or Etro might create more humans in a pitiful excuse for loneliness. And even if there is a finite end, one that Caius can count on, Yeul does not deserve to suffer all the days until its length.
Caius cannot risk that, either. If he is to make an end of it, he must break more than humanity: he must kill the goddess herself, and end Etro's meddling forever.
Shaking on his clothes again, he trudges back to scrutinize the carnage. Only the navidon will be salvagable; the gorgonopsids are a smeared mess of burst guts, the meat so mangled as to be worthless without extensive cleaning. Sighing, Caius crouches on his heels, and checks the sky again.
The day is almost gone. He'd meant to have the water for Yeul's bath to be heated already, so she wouldn't have to do it herself. On a timeline of endless eternity, he is late.
But Yeul would have known what would happen. She would have known what he was doing, just as Etro must. A goddess in Valhalla is capable of seeing everything. If Etro sees everything, then she must have known what would happen when she first set things in motion, placing her heart inside him. And if she knew - then Caius, then Caius, then he.
He must be doing exactly what she wants.
The alternative is even worse.
Anger bucks against his chest - but quiets almost immediately, weighed down by torpid shackles that wrap around his thoughts to keep them steady. Bahamut stirs sleepily, wings shuttering closed in the darkness. Caius, staring at the cooling remains of the navidon, exhales slowly, and reminds himself of dinner.