The dragons in the Chrestomanci series are native to Series Eight of the Related Worlds. Although they are a sapient species, they are at risk from poachers who slaughter them for their blood. Dragon's blood is a highly-prized, not to mention insanely dangerous - and for all these reasons, strictly controlled - magical ingredient; the addition of dragon's blood can boost the power of any spell. In its natural liquid form, it has a remarkably offensive odour and the tiniest amount is lethal on contact; it is usually stored as a dried powder, which is merely insanely dangerous.
In Charmed Life, Mrs Sharp estimates the market value of dragon's blood at fifty pounds an ounce.
In The Lives of Christopher Chant, Christopher Chant gets to see an adult dragon up close. It is a magnificent sight, more than twice the size of a house, purplish-black with bright green eyes. Dragons have mesmerising eyes, like kaleidoscopes.