This ancient order of deadly assassins is an offshoot of the Cult of Tiamat. It was founded during the waning years of the Previous Eon, during which Arkhosia battled both Bael Turath and worshipers of Tiamat from within.
The cultists made overtures to the tieflings of Bael Turath and brought them word of the Dark Lady of Avarice. Some of the tieflings were taken with the message and formed a small cadre of assassins that worked on behalf of the Cult.
It was thought the Wyrmfang order had gone extinct along with the Cult, but evidence of their existence was found by the PCs, who fought them while defending Tulmaster's people's flight from Derlin's Folly. Additional evidence of their existence was discovered the night before the Battle of the Broken Kingdom when a group was discovered trying to sneak into the PCs' camp.