At one point, the head of the clan in the 1870s, Alexei de Quincey, began working for the Pandemonium Club's Magister. Along with this, de Quincey also threw Downworlder parties—the main purpose of which was to defy the Clave and the Accords, accomplished by the deliberate murder of mundanes through the draining of their blood as a show.
Eventually, a defiant member, Camille Belcourt, reported them to the London Institute. The Enclave members then raided one party in 1878. Caught in the act of almost drinking the blood of Nate Gray, brother of then Institute guest Tessa Gray, in front of the guests, Will Herondale lit up the Phosphor, which accidentally set ablaze to the furnishings, signalling the backup Shadowhunters to come. The Enclave rushed into the party and engaged most of the vampires in battle, intending to annihilate the whole clan. After that evening, the few remaining ones, around six or seven, managed to escape to de Quincey's hideaway in Chelsea, in a house near the Thames. The Enclave pursued them the following day, expecting at least a hundred more vampires, after being tipped by the traitorous Nate. Once there, they fought once again and were easily overpowered and killed.
The death of most, if not all, of the members of the clan made Camille Belcourt, known to have been the traitor of her kind that evening, feel threatened enough about her safety that she left the country momentarily after the slaughter.