Maggot (or Grub) Nagas are uncanny beasts with the heads of beautiful women and bloated, white, wormlike bodies. They range from three to six feet in length, and are as likely to be found conversing in the meeting halls of great houses as nesting in the digestive tracts of aging dragons. Whether these unsettling creatures are related to true nagas is unclear, but they exhibit similar abilities--albeit on a lesser scale--and an even more frightening intelligence. They are prized in certain rarefied circles for their unusual insight into the science of governance.
Crunch & In-Play Notes:
Statwise, the Maggot Naga is basically a low-powered version of a water naga--a spellcasting monster with a poison bite; though you might consider giving it a couple gimmicks of its own, like it can automatically turn arrows fired at it into overlong maggots or its bite causes a random mutation.
The real point of the Maggot Naga is to wander around the campaign being both elegant and disgusting. I would role-play it completely straight--as if it's a perfectly sensible young Machiavellian advisor or lady-in-waiting who roams the castle (or chews its way through a frost giant's intestines), talking about grain production rates or discussing who is going to take the ring to Mount Doom that just happens to have the body of a great glistening maggot.
When the local Count invites the PCs for a sit-down about the recent peasant rebellion over dinner and there's a maggot-woman in the next chair articulately arguing the fine points of drought prevention in between face-first gulps of mutton, your players are bound to start wondering whether this regime--or any regime--could possibly be as corrupt as this looks, or whether this is just some sort of don't-judge-a-book-by-its-cover lesson in diplomacy and the grub chick is really just a perfectly nice young lady who has learned to be tirelessly patient in the face of persistent prejudice from superstitious rubes.
Which of these is the truth is, of course, entirely in the hands of the DM.