The Price of Generosity
Little is officially written regarding such infernal reagents, as it is considered heresy or inviting demonic corruption by all but the most powerful or foolhardy. That said, there are those who see demons as a means to power, and have written secret volumes of forbidden knowledge on the practical application of their body parts in ritual magic.
Succubi’s lips can be harvested in the rare event when a succubus actually dies in the mortal plane, rather than simply disappearing and respawning in Hell. When dried and preserved with other magical ingredients the lips can be used as a highly potent aphrodisiac, causing any who inhale or ingest them to break out into uncontrollable sexual impulses.