[DFRPG] Making demons demonic

From https://awesomeliesblog.wordpress.com/2018/04/24/diabolical/ an interesting anecdote, which may be written specifically for that article or possibly from an RPG sourcebook:

In the wake of these defeats Agrippa was consumed by anger, shame and dread. He feared the armies of Talabheim and Middenheim would arrive at any moment to slaughter him and seize the throne at Nuln. His wits perturbed by panic, he sought out Calidus for advice, who presented to him the most desperate and dangerous of measures. To this Agrippa agreed. Calidus called forth the infernal spirit Achorax and the young emperor entered into a most dreadful bargain with the demon. On Geheimnisnacht the demon would destroy the two older emperors, and thereby Agrippa would be left with an unchallenged claim on the Imperial throne. Yet the demon's price was high: the moonlight of that night would also be the last seen by Agrippa's daughters, who would be condemned to an eternity of torment in the Abyss.

The fatal Geheimnisnacht arrived and Achorax claimed his payment. Yet the demon's work was not done in Nuln. Two days before the night of the Twin Moons, the Emperor Konrad had succumbed to a sudden and mysterious illness and the Middenheim throne had passed to his twelve-year-old son, Arnulf. Achorax held to his bargain and that night tore asunder the two older Emperors: Lothar and the hapless Agrippa.

– Dietmar von Humboldt, A History of Sigmar's People, XVIII.43

To me this shows an interesting way to make demons fearful: by making them know stuff. Just like Dresden Files Outsiders always act together, flawlessly cooperating, maybe a good distinction between Tanar'ri and Baatezu could be that Baatezu share knowledge, maybe even magically, so that if you summon one Baatezu to demand power, it knows that Emperor Conrad is dead as long as any other Baatezu knows. It knows where all the bodies are buried.

That could be an excellent reason to be wary of ever signing a contract with one.

This will probably influence how I run demons and Elder Things in DFRPG.