AN: This will almost certainly be jossed before too long, but the idea wouldn't leave me alone. Based on information given in The Revelation.
Masks on Empty Faces
"Ah," says Koh. "A mortal."
A mortal boy. A living boy. A young and breathing child at the yawning mouth of his cave, at the wide-gaping and toothless mouth of his bone-strong sanctuary. His face is round and rippled with the touch of fire, with the curling breaths of pain through flame-touched lips.
"I see you, spirit." A young voice, a young tongue, sweet tender flesh for the taking—
—but a steady mouth, a straight mouth, and eyes that burn with a hatred as old as the stone and the stars and the root-deep sounds of his name. "What brings you here to me, boy-child?" he asks, and bends the long curving pieces of his body to fit the arch of shadow over the place where this mortal crouches. He does not have a scorched face like this, not yet, nor a child's face with such black eyes, dark as pitch, dark as tar.
"Revenge," the boy breathes, small-fingered fists clenched in fear, and rage, and impotence. "No one else will help me."
Black eyes, a straight mouth, a young and tender tongue, and the fire's stone-hard caress in place of skin—an unusual face. A compelling face.
Koh says, "I will help you."
The words are worth nothing, empty bird-voiced chatter, the same unending circle of mortal death and mortal suffering—but Koh is ancient in the way that few things are ancient, and he knows the song that underpins it, the deep and bitter lust for vengeance that consumes from the inside-out, ravenous and never eased.
"They took from me," says the mortal boy to the Devourer.
The needles that are his legs touch together in amusement, flooding the cave with the rapping of long and hollow bones. Koh chooses one face for the ironic twist to the mouth; then another for the deep and mirthless laugh of the unloved. "I will take from you more than I give," he says, a warning and a promise.
The straight mouth firms; the scar-lidded eyes lift. There, no fear; there, no rage: a mask of fire.
"I will enjoy you," says Koh.
"Take what you want," the boy says to he who only takes all. "But teach me."
Koh chooses his own mask, with its red, red lips, and its death-white skin, and he smiles.
In the age before ages were counted, when the world was wild and unfinished and Koh was more blooded man than spirit, he ate.
Flesh, yes, and faces, even then—and strength, and knowledge, and wisdom, that he might know the truth from the things that are not true and so know himself better. Then the first Avatar was made, for Koh is old and was old then, and for the first time in his long life he knew: hunger.
This was a knowledge he had not foreseen; this was a strength that no long-toothed face-eater might eat. He tried, yes, for the Devourer consumes what it loves, but he found himself drowned in a swollen sea and burnt by struck flame, buried in rock and earth and stripped of the breath in his mouth.
Avatar, he learned, and Koh does not forget truth.
They dance together for ages upon ages, pushing and pulling the way the moon does the sea, touching here and there in glancing blows that shape mountains into being and split deep gorges into the earth. Koh eats hard truths and grows hard in return, hard as chitin, hard as the pangs of hunger in his belly; the Avatar changes faces in the easy way that Koh changes faces, consuming the body and pressing the soul into the shell of another. There are times when the Avatar wins and Koh flees to the sunless places of the world to close up his bleeding wounds with rage and black ichor; and there are times when he wins, when he opens the wide and smiling mouth to bare the needle-shine of teeth and takes the Avatar for his own.
But oh, he hungers for more than the face.
The strength does not come, when he tries to eat it; the spirit does not taste; he hollows out a place inside himself for a truth that he has yet to eat and suffers more for the hollowing.
Years pass into years; the dance circles in its endless fiery ring.
Then he learns the river.
They give it a name, the mortals: chi, a short sharp sound like a breaking branch, a word too small for the river of power that moves under the Avatar's skin. He learns it—learns all of it, from the streams and strength held even in the smallest finger to the great root that surges forth between the eyes. There are many mortals now, seeds of the Avatar softened and weakened like chaff in the thin-running blood of her children; they are young and tender and too great to count, too numerous to notice when one here, one there, goes missing and does not return.
Koh has seen rivers; Koh has also seen dams, and over a hundred crawling lifetimes, he teaches himself a new truth: loss.
Ah, but he has always known how to take.
This eaten truth he tells the boy; he shows him, too, with long thin clicking legs and a beast's face, how to dam a river-soul and take its strength for his own. Time passes in the world, but his home is a dark place where time has no dominion, and light has no dominion, and in the black throat of the cave where Koh speaks his truths the boy hungers only for his words.
When he is finished, the boy's tar-black eyes glitter like the small deep flare of a coal's heart before it strikes into flame. "Give me the strength to do this."
"Ah," says Koh, and knows his hunger. "A mortal child may eat a mortal's flesh; a spirit may eat a spirit."
Sweet voice, sweet tender neck, sweet pink and spit-wet tongue that flashes between teeth. "Then give me something of yours—I'll let you take anything of mine—you said you'd help me."
Koh thinks, then, of another young boy, a face as young as this but without scars, of grey eyes and a name that is not a name but a thousand circling lives. He says, "You will damn the soul of the Avatar."
"Yes," the boy breathes, his eyes burning. "Yes."
Then Koh moves, sinuous and smooth as water moves through cupped fingers. He coils himself around the mortal child, unflinching child, touches the tips of his hundred legs to the boy's flat nose, his straight and unmoving mouth, to the dark pits of his hating eyes. "This," he says, "I will take."
"Yes," sighs the boy, and the scarred and rippled skin of his mouth cracks as he flexes muscles long disused and curves his lips—
—into a smile.
"Ah," says Koh, deeply, deeply satisfied, and eats.
When he leaves, Koh chooses from his faces a face of porcelain and paint, a white-bone mirror of his favorite red-lipped mask: a piece of himself, Devourer, hungry, wanting, hollow and wholly ravenous.
It fits the boy-child's face like Koh knew it would, because Koh is old as bone, old as hunger, old as Truth, and he knows when he sees himself.
The dance circles; he pushes; he pulls. The mortal boy looks up at him through the bone-fixed smile of the mask.
Koh says, "A gift."
Koh says, "Take it."