Not many people have ever met this rarity of the djinn; and even less have lived to tell the tale. Those who fought one of them (or, at least, claim to have) say that the marid are fierce warriors who enjoy duels; they appreciate a skilled opponent, and seize any opportunity for a single combat.
Their element, unlike most of the other djinn's, is water. Legend says they used to live in the vast oceans in cities and kingdoms very much like ours; but after the War, most of them disappeared together with their watery realm. (Every once in a while rumors start spreading that one hero or another has met and fought a marid; but since they are said to melt into drops of water when they are killed, there is never any evidence.) Marid were said to be willing to grant the wishes of those who defeat them; but since they lost their freedom to the rule of the Nadir, they seem to be less generous with our kind. I know I would be.
Truth behind the myth
Marid are water djinn in Arabic folklore and mythology. They are associated with salt water, oceans and seas, and some sources claim they are the most powerful of the djinn. They have the ability to grant wishes to mortals who can defeat them, or trap them, or just flatter them enough.
The marid people in the world of Nadirim are a mixture of marid folklore and ocean tales of the ‘sea people'. Several stories in the Arabian Nights mention people who live underwater in splendid cities; they can breathe on the shore too, and grant the ability to walk underwater to those who earn it. In one story (Julnar the Sea-born, 738th night and on) a princess from the sea folk marries a mortal man, and their son belongs to both realms; another tell us about the friendship of a mortal and a merman, and a visit to the wondrous underwater city (Abdullah the Fisherman and Abdullah the Merman, 940th night and on). There are tales of trade and exchange of gifts; they inspired the abandoned marid market at the harbor of Quadim.