Psychomachia
Pious scholars study the Psychomachia of Prudentius, spending countless hours annotating the religious poem recounting a war between virtues and vices. The impious scholars of the Baali bloodline study it as well, but they recognize it as more than an allegorical device. When a Baali ferrets out her victim's greatest failings, she may breathe a demonic life into them, casting her victims as an unwitting "hero" in the morality play of his nightmares.
System: The Baali must successfully use Sense the Sin (above) on the target during the same scene, and then spend a full turn in concentration. The target must roll his lowest Virtue (difficulty of the Baali's Willpower). Even one success is enough to defuse the psychic attack, but the Baali may attempt to continue the assault in subsequent turns. Failing the roll pits the target against his own worst vice (pride, envy, anger, sloth, avarice, gluttony and lust are the classical seven, but many other vices make appearances in the Psychomachia and other popular allegorical literature). The vice usually appears as an important figure from the victim's past - an abusive parent, a scorned lover, a trampled nemesis or (for vampiric victims) a manifestation of the Beast within. The spiritual assailant is visible only to the victim, but to him it is solid and painfully real. Also, any Derangements from which the character suffers immediately come to the fore. A botch on the Virtue roll indicates that the victim has been completely overwhelmed; he frenzies (if possible), or becomes possessed by the manifestation of the vice and develops an appropriate Derangement.
The imaginary assailant is a Storyteller character that can be wholly narrated, or assigned Traits equivalent or slightly inferior to the victim's - though a character whose sins significantly outweigh his virtues should encounter stiffer opposition. (Storytellers note: if you plan to use a Baali with this power, you may wish to prepare an appropriate opponent for each of your players ahead of time. If a player in your troupe has a Baali character, for whatever reason, do the same for characters significant in your story.)
The victim of Psychomachia must defeat his dark counterpart, though not necessarily through combat. he may outwit or cow his alter ego, but accomplishing this isn't likely to be easy - the dark figment knows all of the victim's usual tactics and threats. If the victim attempts to act against the Baali in any way, the imaginary doppelgänger attacks. All injuries sustained by the victim in a physical engagement with the figment are illusory (substitute catatonia or torpor for death as appropriate), and vanish when the opponent is defeated, or when the Baali ceases to concentrate on the attack.