I love a lot of things about the "Infernum" worldbuilding (an RPG about playing in Hell if you never heard of it).
For example enforcing the "9" number on the structure of Hell to play on the Dante's Inferno vibes (nine levels of Hell, nine breeds of demons, nine ruling Houses). Or making the demons the result of mating between the actual, proper fallen angels and the "Hellspawns" which are just the doodles, scribbles, prototypes and failures of God's Creation, Clive Barker-style.
And of course the Nine Houses themselves. Love them.
The seven deadly sins, obviously. The Carthenay for Greed, Riethii for Lust, Sturrach for Wrath, Haimon for Sloth, Lictat for Envy, Zethu for Pride (as in mad scientist/tyrant sorcerer pride) and Oblurott for Gluttony (with them being being treated as a joke, but fully presented as both horrifying in their repulsion and powerful due to being the most ancient house and the one with angelic secrets/knowledge). Plus the two bonuses that are the Astyanath for Cruelty (because everybody needs a Cenobite-like demon house in a hell-themed RPG ; they also technically are the other side of Pride alongside Zethu, more as in aristocratic arrogance and artistic vanity), and the Glabretch for your local Warhammer Chaos nod (don't tell me they aren't Nurgle-inspired).









