Ok so I'm brainstorming a campaign setting.  I won't go into detail. I'm ambitious, I think I could possibly publish it. Even if just as a DM's guild product.

So anyway, part of it involves a cruel and fairly xenophobic society with different clans/houses. Each house has their 'thing'. One house uses 'mongrels' and 'inferior' races as part of their structure. The idea being that this house is the PC's inroad to shenanigans.

I swear to god this is something I've read or encountered before and it's bugging the hell out of me because I can't remember where. A Warcraft expansion? Possibly Legion and one of the Suramar factions. A novel maybe? Chris Wooding's 'The Fade' is really ringing a bell here. Maybe this is some old dim memory from the Drizzt novels or some other Dark elf related setting. Bah, it's driving me nuts. (They aren't dark elves in the setting I'm working on by the way. But that's pretty irrelevant, it's the underlying ideas that are the main concern here)

I don't want to have to replay an entire WoW expansion or reread a novel just to find this out.

Hopefuly someone knows exactly what it is I'm half remembering.

Well, here's a writing exercise I do that I think of as a 1-player telephone game.  You write out the idea that you're afraid you're ripping off and then start changing the nouns.  And you don't just change out the nouns, though, you keep changing them and changing them until some combination actually sparks an image or a line of dialogue or whatever form you get ideas in.  Then write down that idea and explain what it is it sparked in you and develop that idea until you have something you know for sure is original.

Who cares? Nothing is 100% original, and everything is somewhat original. If it's what you want to create, do it. It will definitely be your unique take on the concept.

I care. Personal pride I guess. I dont want to be a lazy writer. I agree that no idea is truly original and my source of inspiration probably got their idea from something else. I'd like to know exactly what the source of my inspiration is though so I can evolve it and make it different and my own.

Ironicaly, checking old scribbles, this might actualy be my own idea I'm remembering from another project I had on the backburner. Which teaches me I really should get earlier stuff knocked into shape before taking on something new.

Imperial based society or something more recent?

Your ruling household does so through a means similar to the Sword in the Stone myth?

For example they've been making use of elven built fortresses left behind when their builders chose to leave the kingdom rather than face eventual extinction as they don't reproduce anywhere near as much as the other races.

So something like a number of various noble houses each having their own dominion who hold court in the capital where their presence has to be maintained to insure their political presence means they can avoid being teamed up on by the other Houses.

However they make use of mercenaries and the Guilds when they can't be seen publicly to be supporting actions that might effect their standing with the other Houses let alone the ruling House.

Introduce certain legends that may or may not effect their leadership, perhaps the new ruler is selected by an esoteric means requiring the location of items or a bloodline that must be kept note of to avoid the current rulers being ejected because they hadn't properly maintained their bloodline properly?

For example the current King earned his position initially through marrying a member of another noble house, but in actuality he had been married to someone of the actual ruling family long thought wiped out.

The High Priest lied about his original marriage being unlawful so when he drew the sword he was still considered married to the true Royal Line.

It was only afterwards that he found he could no longer draw that blade that he suspected something had changed.

He had two kids with his wife, but neither were his biologically, what neither knew was that he had been adopted into his family as part of pact made between his biological father and the head of his House.

Both his older brother and father were killed and his new wife was pregnant with his brother's child.

The second child was born due to his wife being fooled into a relationship by someone using a magical disguise so was unaware of her daughter's true lineage.

The King's only true biological child turns up becomes fast friends with his heir as both loathed him and to make matters worse his ex-wife having figured out what had actually happened arranged for them to renew their vows properly after properly divorcing her as her sympathy was with his new wife!

Then his true son died apparently protecting his daughter, the King suffers a stroke and is more or less at deaths door leaving the entire kingdom in upheaval as the forces fighting for the throne are trying to secure the heir and aren't above ignoring the fact neither are the true heir if they use the same paradign their father used to prove his claim to the throne.

What the OP wants to come up with will probably be more convoluted than this!

Best wishes hope this helped!

Thanks for the effort, though it is off tangent from the original post. Its a shame my setting isnt a more standard fantasy one as lot of those tropes would have worked. However in this instance its factions of a yuan-ti society that are remnnants of an empire wrecked by a self inflicted apocalypse.

I am quite certain now its an earlier project of mine Im remembering and not someone else work. Thankfuly it isnt Warcraft Legion so I dont have to do that again!