Fearsome in Its Parts

A terrible creature ravaged the lands all around. All who saw it gave this description:
"The beast has the head of a dragon, the body of a wyrm, and the hindquarters of a drake!"
The greatest slayers of monsters converged on the kingdom and assayed to strike down the creature in response to the king's pleas (to say nothing of the rewards he promised). The search demanded skill and the battle unflagging courage, but they killed their quarry and presented it to the king before all his people, who objected.
"That is a fearsome creature, certainly, but it has the body of a drake."
"Does it?" the hunters wondered.
"It does," all agreed.
Confused but moved by kindliness and integrity, the slayers sallied forth again and brought down a beast that had the head of a drake, and one with the hindquarters of a dragon, and one that was a wyrm all the way through.
"I am beginning to question," one among them opined when away from the capital, "whether we are not being deceived."
"I have had the same thought," another concurred. "Looking at him, the king's body is not immune to weaponry, and while I have said nothing about it before now, I . . . What is that?"
They saw in flight far off a creature that was obvious in having the head of a dragon, the body of a wyrm, and the hindquarters of a drake, so much so that they marveled they had ever made any mistake about it. Soon they freed the kingdom from its worry.
Finis

Monster Q&A Corner

Q. Why are centaurs partly human?
A. The human ones killed all the goblin ones. Don't feel too bad for them, though. They took out the lizard ones first.
Q. Why are manticores seldom depicted with human faces?
A. Because it looks dumb. God Emperor of Dune is a similar case.
Q. Aren't most manticores in fiction really just chimeras?
A. Hold on, let's not pass over "in fiction." Or "really." Tell us what you know.
Q. Gotta go!

Addendum

The secret is that I just wanted to roll out "thaumatocracy."

Against Thaumatocracy

Given that being capable of magic is better than being incapable, what are some reasons mages might not be in charge?

- There aren't enough of them
-- It requires innate talent which few have
-- It takes too long to learn
-- They keep dying
-- Numbers are limited by the need for some external resource. For example a mage has to bathe in dragon's blood or make a contract with a manticore
- There are too many of them. Being a mage isn't a big deal, and hiring some is less of one.
- Magic isn't that good
- The kinds of people who learn magic are bad at maintaining political power
-- They're too busy with magical studies
-- Magic is linked to certain characteristics such as lack of ambition or gullibility
-- Magic alters mages, for example removing the need for food and replacing it with an insatiable urge to visit places of power
-- Magical expenditure requires long periods of isolation or hibernation
- The kinds of people who learn magic don't want to maintain political power
-- Magical talent isn't hereditary. Ensuring your family will be passed over for some genius discovered in a village is distasteful.
- The kinds of people who learn magic can't maintain political power
-- The gods who give them power forbid it
-- The terms of their contracts forbid it
-- The dragons who rule the world forbid it, and they do check regularly
-- Magic circulates through the bonds between people, so that the more subordinates one has, the more his magic is divided among them - The rulers are capable of preventing it
-- They aren't mages, but they have magic
--- Divine sanction
--- The approval of the land itself
--- Contracts with manticores
--- A store of artifacts
--- Hereditary talents
--- They're the source of magic
-- They're above magic
--- Gods rule directly
--- Dragons/manticores/basilisks etc. rule directly
--- Aliens rule directly (they came to research magic)

There are a few reasons. As for how mages might become an oppressed minority, they can't, cut that out, your allegory stinks.