There is a wound in world, and it is bleeding.

Some understand it. They know that there is a corrupting, corrosive force from outside reality. It has tainted their bloodline but given them the insight to spot its effects. From across the world, brave souls have faced down the corruption and tracked it back to its source.

That source is the castle, a sprawling, chaotic, and ever-shifting gothic nightmare from places unknown.

All that it touches is twisted to nightmare or empowered by unwholesome magic, at the whims of the Natural Philosopher - the castle's Regent. From the moment it tears a hole in our reality, the blood shed by that wound collects in the castle's corridors and keeps, eventually pooling in the Black Grail deep in the Regent's sanctum. When it's full, a grand ritual will blight he land, unless the brave souls can stop them first.

Even if they manage to defeat the Regent, what then? The Grail will remain, ready to work great changes on the world.

The Castle always needs a regent.

====

THE NATURAL PHILOSOPHER
DRIVE: Insight - Understand the laws of existence
STYLE: Artistic, amateurish science. Unfinished work. Long tracts of creative labor made by an unimaginative mind and iron will.

The Natural Philosopher was never of letters or learning, but of practical things - hard work and dedication. When burgeoning scientists told her the universe was governed by laws and physics and the abstract, she dedicated her life to proving them wrong. The world, she knew, must be governed by simple, plain, clean laws.

She refuses to believe otherwise, and has consorted with powers unknown. With the power of eldritch geometry she warps the castle into being, and soon she will warp the laws of reality itself to fit her vision of what should be.

QUALITIES

THE FIRST LAW
The Philosopher is surrounded by an aura that prevents death.
--Prevent death until her riddles are solved.
--Manipulate the rules of gravity, strong, and weak force.

WILL OF STEEL
She fills the halls with paper and art to her own brilliance.
--Animate her creations to protect her
--Speak to the explorers from afar

EMPLOYEES AND STAFF
They ask for overtime no more.
--Deafen with chants
--Grab an explorer

TEAR AWAY THE UNTRUE
The Natural Philosopher burns away the false, leaving only essential truths - that she is right and the universe is wrong.
--Grab an explorer
--Fill a grabbed explorer's veins with obedience and fire

UNWHOLESOME DEALINGS
She consorts with things she should not, bringing semi-sacred geometry to the fore.
--Cause madness
--Summon eldritch fiends

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Rhapsody of Blood is a fun tabletop RPG with a lovely little expansion module called Rhapsody of Blood - Terra Incognita . It's a mix of Darkest Dungeon and Metroid and Castlevania using the Powered by the Apocalypse ruleset. Quite good fun, though I admit I've not yet finished the game!

During quarantimes, I played around with the Terra Incognita booklet to create a fun castle (with a few kinky elements here and there.) [For instance, Nobody can really die in the Castle; she doesn't understand it, and she wills it to not happen. Natural laws and all that don't apply to her! ]

A lot of work was done by PKTT and Spirit-of-Vice and got some great inspiration for the Eldritch ward (the purple area) by VoughtVindicator