The deep dragon is a fantasy monster.
They are almost completely unknown on the surface world, as they live in the underground world known as the underdark. They stay deep underground for their entire lives, rarely having the opportunity to run or fly. In fact, many of them have never even used their wings.
Deep dragons can assume 3 forms, and they are equally comfortable with each one. The first is standard dragon form (they may be anywhere from 20 feet up to a hundred feet or more in length). The second form is that of a large winged serpent (size varies, but always much smaller than dragon size). The final form is that of a human (or humanoid). The deep dragon is most commonly encountered in human guise (a cunning deep dragon can transform into the appearance of many different races, often with enough skill to masquerade a specific person).
In dragon or serpent form the deep dragon will be covered in irridescent maroon scales (while they can have any look they want in human form). They travel the underdark widely, exploring caverns, and amassing treasure. The deep dragon will keep his treasure spread out among many lairs and hiding places (unlike surface dragons, who prefer a single hoard). This is because of the deep dragon's unique environment. The underdark is highly populated with many races. A surface dragon has little fear that someone will wander into his lair when he is not around. But a deep dragon cannot expect that (between the wandering adventurers, expansionist drow elves, and all the other underground races, it is only a matter of time before someone comes waltzing in the front door).
The deep dragon is a formidible opponent in all forms (and without the big treasure payoff that comes with most dragons). They have the ability to alter the stone around them, regenerate quickly from damage, and have a breath weapon of toxic gas (which they can use in any form).
These dragons often cooperate with the local (and not so local) drow elves (usually in a mutual defense type agreement). Some deep dragons masquerade as other races and will live with the drow or deep gnomes for years in disguise. Although some surface dragons that can change form have been known to do the same thing (this is the dragon equivalent to taking a vacation).
<----------------------------------------------------------------------------->
<----------------------------------------------------------------------------->
<----------------------------------------------------------------------------->
<----------------------------------------------------------------------------->