Seriously, there are way too many "the king is a thingy" or "the king is controlled by a thingy" ideas here. We could probably combine them all and prune the list from 50 to 15.
I took a class on conspiracy and paranoia in college; it was great because the final paper I wrote my senior year was about The X-Files. Allow me to adapt some real-world conspiracy theories.
53. To aid in the production of magic items, the royal magical treasury must acquire the life essence of humans. They do this by sending out agents disguised as healers to rural villages, farms, and thorpes. The 'healers' treat the sick by day, but no one ever really gets better. At night, however, the agents sneak into the homes of their patients and extract all their vigour, in the form of fat. The fat is then delivered back to the cities.
Why else would all the people in the cities be so healthy and plump, while the folks in the wilderness are so often sick and malnourished? (From an actual 'vampire' conspiracy in South America.)
54. Recently a powerful demon was summoned inside a once-peaceful city, killing thousands of innocents and destroying prominent religious structures before it was banished. Divinations all point to the demon having been summoned by drow agents who want to destroy the kingdom because of its alliance with the surface elves. The kingdom has now enlisted the aid of other countries, including the surface elves, to strike back at the drow.
In truth, however, the entire event was a sham. The demon was an illusion, the 'high clerics' who performed the divinations were either in on the conspiracy or were deceived themselves, and the drow were not involved at all. In truth, the kingdom had already killed all the innocents due to another project gone awry - a magical machine intended to mind control the populace. When all the test subjects died, the government needed a way to conceal their culpability, and so this hoax was concocted.
A few truth seekers tried to get the message out, by they were silenced, and have not been seen for weeks.
55. A special magical minting press was created, which imbues the coins with a contingent spell. Only one out of every thousand coins has this spell on it, but it is heavily concealed, and utterly secret. Whenever a coin so enchanted passes into the possession of a foreigner, within a day it will teleport back to the royal vault. This allows merchants of this kingdom to trade with merchants from other lands, without the kingdom having to give up any of its own money.
56. Two thousand years ago, the god of healing died. The rulers of every country are descendants of the group of adventurers who killed him, and they have gone out of their way to ensure that their ancestors' sin remains concealed. Even the gods themselves have been fooled, because the coalition of rulers found some other entity to pick up the slack of the fallen god.
57. A few mages from different wizard schools vanish mysteriously every year. Each of them was working on magic somehow related to teleportation. Is it simply a hazard of the field, or is the government trying to stop those who might unseal the nation's borders?