Dark Passions are the core emotions that drive a wraith's Shadow.
Just as a wraith can gain Pathos by acting on their Passions, their Shadow has Dark Passions that generate Angst. Sometimes these Dark Passions are parallels or even inverses of the wraith's regular passions: destroy the thing the wraith wants to protect, for instance. The Shadow benefits whenever it has the change to act upon its Dark Passions directly, or when the wraith acts on them (whether or not the Shadow has done anything to provoke it). A hue's Shadow uses its Passions as Dark Passions.
The Castigate Arcanos allows the user to learn a Shadow's Dark Passions and even try to reduce their strength. The Way of the Soul also gives Eastern wraiths tools for managing their p'o, including replacing one of its Dark Passions with a regular one. The highest level of this Arcanos allows the temporary reunification of the hun and the p'o, with the wraith gaining Pathos from both its regular and Dark Passions.
Spectres also have Dark Passions, and strong ones provide it a measure of status within its caste. Shades in particular are defined by their Dark Passions. The Dark Arcanos of Larceny allows spectres to infect others, including mortals, with specific Dark Passions.