Astral dragon

Astral dragons were rare and powerful planar dragons native to the Astral Plane.

Birth, development, and reproduction
Every few hundred years a female astral dragon could lay one egg, which was about in diameter and the same color as the rest of the Astral Plane, making it difficult to see. This egg grew, over many years, until it was in diameter, at which point a hole opened at one end. The egg itself became the hatchling's lair, and it continued to grow to a maximum of around in diameter, at which time it was very thin (although still strong).

A young astral dragon used the egg for storing treasure, much like a regular lair, and established a mental link back to the egg, to find it later. Once adulthood was reached, the egg was abandoned in favor of a larger lair, and these eggs were often taken over by other species.

Younger astral dragons spent more time on the Prime Material Plane than their adult counterparts, and the older the dragon became, the more time they spent on their native Astral Plane.

Astral dragons only grew to around in length ordinarily, but that changed when two of them mated, at which the pair increased in power and size (growing to  in length), and a magical chain appeared which bound the two together. The chain could extend up to and said to be a sign of their devotion to one another. Astral dragons considered this chain a blessing. Additionally, mated astral dragons made huge palace-lairs which they rarely left, but were close to demipowers in might in their domains. To gather information, they would send out kodragons instead.

Habitat
Astral dragons take root in the vast expanses of the Astral Plane.

Lair
Once astral dragons have outgrown their egg, young dragons usually resided in floating debris like large skulls, but older dragons would usually reside on the floating islands in the Astral Plane.

Religion
Being in close proximity to the realms of the gods, they deeply respected the dragon pantheon.

Personality
Astral dragons were quite xenomisic to anyone they didn't view as native to the Astral Plane. They prefer to banish interlopers rather than kill them as the bodies of the victims they have killed were just considered otherworldly clutter, or even just to prevent the attracted presence of an astral dreadnought. Astral dragons dislike being in the Prime Material Plane and they would agree to almost anything to avoid being bound to it, like being captured and imprisoned in the material world. They live for their own personal freedom, that even a promise between them and a non-astral native is something that they avoid because they feel that promises tie them down to a non-astral entity and their plane.

Astral dragons, like some other dragons, had a desire for treasure, and sought to acquire it by traveling the planes. A favorite target was githyanki, since they tended to have magical, gem-encrusted armor, but an astral dragon also enjoyed treasure acquired from astral travelers. Magical treasure recovered from an astral dragon's lair on the Astral Plane appeared normal unless it was returned to the Prime Prime Material Plane.

Diet
The astral dragon did not require very much food, but they did enjoy eating, preferring githyanki where possible.

Disease
Some astral dragons contracted a disease known as astralomitis, which inhibited their ability to travel the planes, and was more common amongst astral dragons who switched between planes frequently. If a dragon was on a non-native plane when struck by this disease, it was unable to return, and there was a chance that insanity would ensue. It lost the ability to cast any spells in this state, but ferociously attacked any creatures nearby. This state could last for up to five days, and resulted in the death of the dragon. If it could return to the Astral Plane by this time, the insanity slowly diminished, but it was left unable to switch planes. The disease had no known cure except for a wish spell.

Abilities
Astral dragons could see through the blur of the Astral Plane for up to 10 miles (16 kilometers), and could plane shift at will. They were able to fly on the Prime Material Plane thanks to an organ in the head, although they were not easily able to walk under the effect of gravity. The dragon's exotic flight organ negated the subject of gravity and substituted the area around the dragon with a null gravity field around itself for up to 30 feet, and the null gravity field would get larger as the dragon got older. This null gravity field usually incapacitated other beings' mode of transportation when near the dragon.

When traveling to the Prime Material Plane, they tend to not stay very long as they were not adept to gravity, compared to the gravityless realm of the Astral Realm. Their flight becomes sluggish, and their legs were not developed enough to even support their own weight, giving the impression that they squat everywhere when grounded, and weighted body parts like their tail would drag along the ground.

Most astral dragons were knowledgeable in magic, with them knowing as much as a novice wizard, so they're fully capable of learning ritual magic, crafting magic items, as well as acquiring spells, and researching new ones.

Combat
In a battle against creatures not native to the Astral Plane, the astral dragon would prioritize attacking spellcasters, since they might be responsible for keeping their companions in the Astral Plane, so killing them would defeat the entire group. They were capable of a nasty bite, comparable to the deadly bite of a red dragon, and they were able to occasionally sever the silver cord that bound beings to the Astral Plane. With its 80-foot long serpentine body, it would attack with its four claws or its needle-like spiky tail. Their resilience was comparable to the copper dragon, and they were usually capable of being resistant to any form of magic that would hurt them half of the time. When it came to fighting beings of a magical or psionic nature, they were usually advantageous, given their natural affinity to those kinds of effects. They were also resilient to being swayed or charmed into doing the bidding for others.

Historically, they have had three breath weapons. One genetic strain of astral dragons used a line of magical force that would usually push their enemies away, depending on how large the being was. Usually, huge creatures were advantageous in resisting the knockback, but tiny creatures were extremely susceptible to it.

There was a second genetic strain of astral dragons that would use two kinds of breath: a line of dismissal, or a cone of scouring dust. The line of dismissal consisted of magical energy capable of banishing another being from the Astral Plane. Usually, the being is sent to their home plane if they were a visitor, but occasionally it would send a being to a being to a completely different plane of reality, different from the Astral Plane or their own home plane. The cone of scouring dust consisted of dust, sand, and grit that caused a stabbing sensation, and would make their victims incapable of seeing.

Although an astral dragon had no psionic abilities, it could sense psionic abilities in others, up to around 240 feet (73 meters).