When it comes to the mother of all evil, Mrs Coulter, chief antagonist of Philip Pullman’s His Dark Materials trilogy, is a serious contender for the title. A charismatic fusion of archetypes - stepmother, fairy godmother, wicked witch - she distils pure terror into the shape of “a beautiful young lady whose dark hair falls shining delicately under the shadow of her furlined hood”. On the outside, she’s just the sort of groomed, sophisticated parent a motherless pre-teen might wish for, but Metatron, the Regent of Heaven, has her measure in The Amber Spyglass:

Corruption and envy and lust for power. Cruelty and coldness. A vicious probing curiosity. Pure, poisonous toxic malice. You have never from your earliest years shown a shred of compassion or sympathy or kindness without calculating how it would return to your advantage. You have tortured and killed without regret or hesitation; you have betrayed and intrigued and gloried in your treachery. You are a cess-pit of moral filth.

Foul as she is, Mrs Coulter remains endlessly fascinating, chiefly for the compelling contrast between interior and exterior. She’s bad to the bone, so corrupt that Metatron himself can’t spot the last deceitful spark of self-sacrificing love buried under the compost-hot layers of murder, sadism, ruthlessness and manipulation that make her up. And moments after he has seen her “naked, body and ghost and daemon together”, in every awful particular, she contrives to seduce him. Even Shakespeare’s Richard III, wooing the widow of the man he murdered – by the bier of another of his victims – might struggle to better that.

She and her daemon, the inner self manifested as an animal companion in the world of Northern Lights, make a fearsome double act. Her golden monkey’s fur is enticingly shiny, Mrs Coulter herself perpetually young, innocent and alluring. (Her prepossessing exterior comes in handy when she’s luring children off the streets on behalf of the General Oblation Board, who will cut away their daemons, maiming them for ever or killing them from the shock.) Even Will Parry, Lyra’s best friend and champion, who has good reason to fear Mrs Coulter, falls under her spell when he meets her for the first time. But woe betide those blinded by her beauty, which is almost literally skin-deep – one of the most frightening things about her is that she smells “metallic” when she’s angry, as though a secret interior furnace blazes up, burning off her soft outward semblance.

Mrs Coulter is not just a pretty face; she possesses a trained, formidable intelligence. She is a member of St Sophia’s College, and can intuit the workings of complex machinery as rapidly as she can read a room. But where other female Scholars incur Lyra’s disdain by being dowdy and pea-hennish, apparently second-best, Mrs Coulter is sleek, sophisticated and the height of good ton at all times. She knows instinctively what is right, like a terrifying otherworldly Nancy Mitford – and she uses this knowledge to maintain her position at the heart of whichever society she inhabits, unfazed by transition between worlds (and swapping lovers like gloves to match an outfit). One of her earliest conflicts with Lyra arises over the “absurd” shoulder-bag that her daughter refuses to take off for a party: when Lyra persists in wearing it, Mrs Coulter’s daemon tortures Lyra’s with a chilling, psychopathic remoteness:

…he took one of Pantalaimon’s ears in his other paw and pulled as if he intended to tear it off. Not angrily, either, but with a cold curious force that was horrifying to see and even worse to feel.

Mrs Coulter has only two weaknesses. One is her blinding desire to be on the winning side, which leads her to throw in her lot with the brutal, muscular Magisterium, rather than to explore the properties of Dust and the new worlds it unlocks with Lord Asriel, the only person (other than Lyra herself) with whom she might be evenly matched. (Lord Asriel is one of the very few characters ever to call her “Marisa” – otherwise, she retains her honorific at all times, remaining distant, elevated and intimidating, with a hint of widowed respectability, despite her chequered past. Asriel, brutal and unsentimental as he is, becomes “father” in Lyra’s lexicon soon after she learns the truth of her parentage – but “Mrs Coulter was never ‘mother’”. That would be unthinkable.)

Mrs Coulter’s other weakness is Lyra: the daughter she abandons, imprisons and relentlessly pursues, product of a passionate affair with Lord Asriel which left her husband dead and her own lustre dimmed. “Coarse and vulgar”, half-taught and indomitable, Lyra “draws” her mother’s poison, “takes her teeth out” with a love that comes “like a thief in the night”, a “mustard-seed” whose “little green shoot” splits open her heart. At first Mrs Coulter attempts to mould her in her own semblance; then, when that fails, to keep her drugged into compliance in a remote Himalayan cave. She even toys with the idea of allowing her to be killed, so that she will not fulfil the destiny which threatens the existence of the Magisterium – but, ultimately, “lying with her whole life” to do so, she sets her daughter free.

Mrs Coulter is a truly memorable villain, a mother-shaped monster of deceit and cruelty who, pace Charlotte Higgins, makes Medea look like a National Childbirth Trust leader. Her intelligence, savagery and utter lack of scruple make her incredibly satisfying; she’s a huge part of what gives the trilogy its lasting impact. After all, who else could have produced a heroine as fierce, tough and adaptable as Lyra?