AN: Not a headcanon exactly – just an experiment with an idea. Feedback welcome.
Disclaimer: I don't own Narnia. I can't even find my copy of the 1988 BBC serial version at the moment.
Jadis dies, but at the moment of her death, she rages – I am Queen of Narnia, and none shall rule here but me! – and her hatred is so strong, so bitter, so concentrated, that it leaves an impression, an echo. A brand upon the kingdom. The superstitious might call it a curse.
The echo gathers its hatred, feeding upon its own anger, and Queen Susan of Narnia takes ship for Calormen with her brother, moved by the ardour of her Calormene suitor. Calormen will take Narnia, and the Tisroc will set a Governor to rule it; but the Governor will grow power-hungry and insubordinate, and the two in their struggles will destroy each other.
Two fleeing children discover a plot to invade Narnia and a safe road through the desert. Queen Susan and King Edmund escape in the night, and the Calormene forces are turned back at Anvard, where Rabadash receives his just punishment. The echo snarls, and no-one hears it.
Thwarted once, the echo's hatred grows, and the echo grows strong on it. A white stag comes down out of the northwest, drawing the Four away, back to their own land where they are but children. Narnia is left leaderless and plunged into confusion. The echo laughs.
A foreign people, from Telmar, enter and overthrow Narnia and set up their own Kings there. Over the centuries the echo gathers its power, building corruption after corruption into the Telmarine court, until all its poison is brought to fullness in the tyrant Miraz. Old Narnia will rise in rebellion, with the support of alienated Telmarines, and in fighting the oppressor destroy itself.
The Kings and Queens of old return, called back by Queen Susan's own horn. With their counsel and courage, the small rebel force led by Prince Caspian defeats Miraz, and Narnia is ruled by a true Narnian King once more. The echo fumes silently.
The mind of King Caspian X is seized by the idea of a noble quest, to seek out the seven lords Miraz once exiled. The echo smiles, inasmuch as something without form can smile: he will die or be enslaved, and the Telmarines and Old Narnians, without their king to unite them, will return to chaos and bloodshed and war. Sooner or later, Narnia will fall from within.
Three children join Caspian on his quest, and he returns from the Silver Sea with a bride and the name Caspian the Seafarer. The echo's fury reaches unsurpassed heights.
A witch comes down out of the north, lured into Narnia by the echo's hate; a star's daughter dies and a king's son is captured. Without Rilian, there is no line of succession. Narnia will fall, to itself or to Calormen. Hope is almost gone entirely. The echo feels what pleasure something created out of hatred is capable of.
Two children are led to Narnia by the Lion, and with a Marsh-wiggle they free the lost Prince and bring him home. Not even the giants of Harfang can stop them. The echo seethes, wringing its shapeless hands.
It is weakened by so many recent defeats, and Rilian's line lasts for seven generations. Then the echo snaps sharply back, more powerful than ever – elastic recoil – and, strong in its formless hatred, breathes a foul and unholy idea into the mind of an Ape. The Calormenes enter Narnia, and evil is done in the name of Aslan, while King Tirian is tied to a tree as a traitor.
Two children return to loose the King and aid the forces of Narnia, but this time they are no match for its enemies. The echo laughs and screams and shrieks with terrible, bloodthirsty joy as Tirian and his companions enter the Stable. Surely now Narnia will fall to Calormen, and Calormen to itself. And none shall rule here but me!
Then the stars rain down from the heavens, and the echo howls soundlessly as it is drawn inexorably into Aslan's shadow.
And then – no more.
Fin.