In His Dark Materials season two opener ‘The City of Magpies’, Lyra and Will find themselves in a new land. Cittàgazze is deserted but for a group of children left to fend for themselves after their parents came under attack. Some adults fled the city but others were caught by the Spectres, who drained them of the spark of life and turned them into blank-faced automatons, like the man Lyra and sees numbly and absently refilling a water jug in a city square. Spectres are invisible to children and only attack post-pubescents. They’re said to appear to adults like a malevolent shimmering disturbance in the air:  “In some lights they were hardly there at all, just visible as a drifting quality in the light, a rhythmic evanescence, like veils of transparency turning before a mirror.” – The Subtle Knife

What do Spectres want?

Warning: major book spoilers below If you’ve read Philip Pullman’s books on which the BBC/HBO series is based, you’ll know that Spectres feed on Dust, the mysterious substance at the heart of this story. As illustrated by Lord Asriel’s photographic experiments, Dust only surrounds adults and not children, explaining the Spectres’ choice of victim. The Magisterium views Dust as evidence of Original Sin (a tendency towards evil shared by all humans, inherited from Adam and Eve’s Fall in the Garden of Eden), and want to eliminate it to keep people in a state of childlike innocence and purity. That was the purpose of Mrs Coulter’s barbaric experiments to separate children from their form-shifting Daemons before they settle into a single form and attract Dust.   Lyra, being a clever sort, has sussed out that if baddies like the Magisterium think Dust is bad, then perhaps it’s actually good. She’s yet to work out quite what Dust is but, aided this season by an Oxford scholar, is on the path to finding out.  When a Spectre attacks an adult to feed on the Dust surrounding them, they eat their victim’s soul (which in Cittàgazze is inside and not in external daemon form) leaving them in a zombie-like state worse than death. That’s why the post-Spectre-attack man Lyra and Will meet is so similar to the post-Intercision Billy Costa: both are soulless. That explains why, as is later revealed, adults who have been cut from their daemons are immune to Spectres. When Lord Asriel used the energy generated by separating Roger from his daemon to open a window from his world to Cittàgazze, the act created a great many Spectres who lay waste to the adults of Cittàgazze.

Can Spectres be killed?

Not by humans, though Will does manage to defeat one by stabbing it with the Subtle Knife of the second book’s title, known as Æsahættr. Will’s mystical knife repels Spectres, protecting its bearer from attack. Angels are also able to destroy Spectres.  His Dark Materials season 2 is airing on Sundays on BBC One and starts on Monday the 16th of November on HBO.