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https://moordereht.com/product/the-pundit-files-issue-29-the-diabolist-class/ (https://moordereht.com/product/the-pundit-files-issue-29-the-diabolist-class/)
I recall in you having some reservations about giving players the assassin class option in Heroes & Villains of the silk road? due to two primary reasons. 1. Historical context of assassins for the setting being tied to a specific cult, and 2. the complications that causes in a party when a PC has such strong obligations to an in-setting group.
I feel like the Diabolist run aground on the same issues you outlined before, given they answer to an actual evil demon lord, and have literal demonic powers. not some milquetoast warlock archfiend nonsense, actual Infernal Demons from a Christian angle! What changed your mind or caused the pivot?
The issue with the assassin was that I didn't want to have it in the Sword & Caravan setting book so as not to give players the idea of playing one that wasn't actually an assassin anymore, or who was, essentially just to wreck the party at some point.
The Diabolist class is meant to be mainly for NPC villains, I would not put it in a main rulebook; but I recognize that someone might want to run a villainous party.