Similar to ghosts, there is an air of specificity about dullahans. They are drawn to specific places, families, or even individuals (“Ichabod Crane!”). So solving the reason for their manifestation can be an adventure seed in itself. As well, they offer complicated moral choices for good-aligned PCs—since they often come for evil-doers, there exists a temptation to let them go about their bloody work…but they also claim souls who might otherwise have repented and reformed, and they slaughter any innocents who get in their way.
For more than a fortnight, a dullahan has stalked the streets of the city, claiming a head a night. Survivors report seeing the dullahan wielding a foreign weapon: a nine-ring broadsword (Ultimate Combat 130–131, 132). Deciphering the mysery of the blade may be the key to deciphering the dullahan’s fell purpose.
Once every twenty years, a Coach of the Silent comes to the castle at the heart of Linden, demanding the lord take a ride. There is no refusing the magical call once uttered. When the carriage returns before dawn, the lord reports having no memory of what has occurred—when the lord returns at all. This year, through an accident of fate (picnic, lightning), the lord is only an infant, and the queen regent is determined her son will not heed the dullahan’s call.
Sometimes the boundary line between the fey and spirit worlds is fine indeed. Gan ceanns are nearly identical to dullahans, but are unseelie faeries rather than true undead. These dullahans have the fey creature template (Bestiary 3 116–117), but have DR 5/gold rather than cold iron—the touch of gold is an anathema to a gan ceann.
—Pathfinder Bestiary 2 111
If you saw what I did there, you’re going to do fine on your GRE.