What's this NPC's secret shame you can blackmail them with if you find out? (1d10):
1. They stole a dead relative's impressive stories they were told as a child as their own.
2. They were castrated (or the nearest genital-equivalent) in a drunken fight in their youth.
3. They subordinate all their important decisions to the advice of an older friend, priest, or other authority figure, leaving nothing significant to their own flagging will.
4. They deal addictive, degrading drugs to support a materialistic quality of life they can't sustain on their own merits.
5. They've got a birthmark in the shape of a blasphemous symbol they don't allow even those closest to them to see.
6. They've stolen another's identity as their own belongs to a persecuted minority group.
7. They're compulsively sadistic, and kidnap & torture others' pets to satisfy their urges.
8. Their own intolerance was the cause of their dear friend's suicide.
9. They're cheating on their spouse with their spouse's sibling.
10. They were intimidated into covering up for a bully's gruesome crime.
A daemon is properly understood not as a being in itself, but rather the manifestation of a force, or mode of intercession, between gods and humans, the celestial and the terrestrial. Love was held by Plato to be a greater daemon.
What happens when one side of that interaction collapses? As a less-theological comparison, imagine if you took a bar magnet, snapped it in half, and were left with a north and a south magnetic pole with no connected opposites - a couple of magnetic monopoles. Now, what these monopoles could actually do is hard to suss out, because according to many models of physics they're supposed to be impossible. Discussing impossibilities can quickly get obtuse, but that's essentially what happens with a one-sided daemon: the impossible, what neither magic nor science could achieve by mortal hands.
When ancestral idols left to gather dust, when a god devours its people's last foodstuffs as sacrifice, when a ruling archon is tossed down from their starry thrown, so too do the daemons tied up with them become one-sided, unmoored, castaway. The room in that ancient, buried complex that blocks all spells, or inflicts unnatural terror, or has its gravity reversed - these could all be castaway daemons, or perhaps stranger things still. If the former, they are snarls that could be unwoven through research into their origins, and then grounded once more and undone, or finally severed and plucked and sold to the highest bidder. After all, the impossible is rare, and thus truly precious.
TL;DR: Why is there weird inexplicable magical effects in the dungeon? Castaway daemons.
Here's a little present for you:
If you've got eyes that can see and a heart that loves truth, you will recognize that this is incontrovertible evidence that Minoan kings were waited on by a harem of renamons.
History as we know it is a lie. Anime is real. Waifus are real.
This is what they took from you:
Under the government of Enver Hoxha, the People's Socialist Republic of Albania became covered in bunkers and run through with thousands of kilometers of tunnels - a hedge against invasion and nuclear annihilation.
In this riot of construction, it should come as no surprise that some people became lost within it. One such person was an officer of the secret police force, the Sigurimi, who on a routine inspection was sealed inside an incomplete tunnel section by an overly-competitive rival.
It can't be said for certain how long that man was stuck down there alone in the utter dark. When that section was opened again his corpse had had time to mummify to a stage that the coroner who examined him claimed should've taken a century given the environment, and every available surface had been scratched with convoluted ramblings. These ramblings took over a thousand pages to be transcribed in full - which they were, by an unknown party.
This transcription was released in a very limited printing to the cultural fringes of Southeastern Europe under the title Libër Nate Pa Fund, the Book of Night Without End. Most of what survives of the Book to the modern day are amateur translations, and partial quotations in fringe academic journals aiming to prove it a forgery. Massacres have been committed to acquire a few pages of an original printing.
The Book speaks of a universe long-before and quite alien to the one we know - one in which the sun and stars were intruders. This universe was ruled by a gentle homeostasis, wherein the scarceness of energy led to a cosmic preference for the intellectual and spiritual over the physical. Its organisms did not - could not - consume and dominate each other, but rather united in collaborative projects through manifold chains of logic over slow eons.
And then there was light, but these peaceable precursors did not take this lying down.
The light invigorated them even as it annihilated them. Unimaginable trillions turned coat, spreading photosynthetic wings to fly across the widening voids and devour their compatriots for mass-energy. Their greatest mind looked forward, so very far forward, for a solution. The stars couldn't be reasoned with. When questioned, they only roared. To preserve anything worth preserving, much would have to be sacrificed. In this initial exchange, 99.9999999% of everything was lost. They'd survive in the nothing left behind, the nothing between atoms and the nothing between galaxies.
This incredible history takes up only small fragments of the Book. It's interspersed in long sections of that lonely man chronicling his descent into starving, hallucinatory wretchedness. In the English copies, there is more word count dedicated to how to eat rat skins without getting too much fur in your mouth. And yet, as the Book itself says at many points, silence can be just as effective at communicating as noise. Acolytes of the Book believe its written words to be a misdirection, a cipher for the true Book which lies in the empty spaces and unused syllables. These acolytes tend to be passionate in their interpretations, as people who come into contact with the Book have a tragic tendency to disappear without a trace.
Whatever the truth of the Book's mythic history, a war is being fought. Memory decay, negative quantum fluctuation, entropy - all theaters of that war. The missing original printings weren't burned, or torn up, or tossed out with the garbage. They simply disappeared. The I Ching's confirmed it. People kill over the Book because a complete copy might hold the key to turning the tide of this war, or at least saving one's own skin. Even if it can't, a human death, no matter how bloody, must still be preferable to disappearing into the clutches of those vast, cold, and hollow things that have had since the edge of eternity to consider their vengeance.
1949: The Dragon's Head is bought at an antiques auction in Wyoming by one Mr. Taboulliet for the sum of $5,000.
1957: Mr. Taboulliet is murdered in his home in a breaking and entering gone wrong by a then-teenaged Mr. Clark. The Dragon's Head is taken, along with a stash of stolen jewelry that Taboulliet had hidden within the fiberglass insulation in his attic.
2015: Mr. Clark is arrested during a Friday Bingo night at his retirement home for drug dealing, pimping, and scamming his fellow residents out of their savings. Shortly before the police search is room, the Dragon's Head is taken by a staff member, his former collaborator, who sells it to an anonymous buyer for $250,000.
1525: The tactical advice of the Dragon's Head allows a Saxon
Freiherr fighting in the Great Peasants' Revolt to lure a peasant force
into a slaughter, winning him personal commendations.
1840: A Ms. Bartlett of Cheyenne, Wyoming inherits the Dragon's Head from a distant relative, and is convinced to fake an identity as an Underground Railroad contact in order to waylay, rob, and murder escaped slaves.
1935: Descendants of the Bartlett family, long indoctrinated into their Satanic family cult by the Dragon's Head, commit mass suicide in their basement alongside the fellow cannibals they'd picked up over the dust bowl years.
1813: A British officer of an Independent Company of Foreigners by the name of Bartlett is egged on by the Dragon's Head to outdo his own men in their brutality. He considers the Head to be his only friend, it having saved his life on several occasions.
1799: The Dragon's Head is looted from the Van Riesse's ancestral estate by officer Bartlett during the Anglo-Russian Invasion of Holland. The Baron Van Riesse's final act is to ensure the whole place burns to the ground.
1760: Then a young man, and not yet baron, Van Riesse is gifted the Dragon's Head by a man staying with family friends who claimed to be the Comte de St. Germain. An aficionado of the morbid and arcane, Van Riesse becomes a recluse, obsessed with the Head's secrets. At first he believes he can exercise the evil spirit within it, but in a moment of weakness after losing his parents to typhus he is convinced to study its dark arts in the hope of preventing any further tragedy.
This is almost total bullshitting on the Head's part to begin with, but nonetheless over the decades it makes great strides in re-inventing the same magics that created it from first principles. Van Riesse becomes a prolific serial killer under its guidance, hiding the remains of his victims in the floorboards of his estate.
1602: A priest seals the Head within a church near Radeburg.
1625: The church holding the Head is sacked by Protestants during the Thirty Years' War, and the Head is unleashed once more.
1458: A student of Nicholas of Cusa acquires at great personal expense the fossilized head of a Lilienstrenus specimen, a basal neotheropod dinosaur that lived approximately 210 million years ago during the latter part of the Triassic Period in what is now Germany. Lacking any knowledge of paleontology, this student came to believe that the skull was that of a dragon, and no less a dragon than the Biblical serpent that tempted Eve into eating of the Fruit of Knowledge of Good and Evil.
Ecstatic with this discovery, the student set about modifying the skull in accordance with the alchemical and necromantic procedures by which his own mentor and Roger Bacon were alleged to have created their brazen heads which dispensed their knowledge.
By luck, genius, or some combination of the two, the student succeeded far beyond the meager results of his predecessors. His brazen serpent was no mere occult toy, but a full, independent consciousness. Unfortunately, it was also under the delusion that it was a being of pure evil whose only purpose was to tempt humans to sin. It had no particular power or knowledge to do so, but it was a quick learner.
1463: The student is murdered by passing drunkards after they're mocked by the Head, which he was carrying in a sack on the way to find buried treasure (which of course didn't actually exist).
2020: After years of mind games and cultic initiations it made up on the spot, the Dragon's Head convinces its buyer to fund paleontological digs in Germany to find more specimens of its kind. It believes it can now fully reconstruct the methods of its own creation.