Koibra are four-legged reptilian creatures the size of big cats. They have long necks ending in snakelike heads with frilled hoods which can be flared out like their namesake snakes, and their bodies are covered in a layer of smooth scales. They have lithe, muscular tails, nearly as long as their bodies themselves, which end in elegant frilled fins.   Their mouths have fangs like those of snakes, with jaws that can unhinge to swallow prey whole. They posses forked tongues, which they use to test the air and which aid a pair of long, senstive carplike barbels in sensing their surroundings.    Their limbs are squat and stocky, but powerful, and, aside from th flowing finlike frills which protrude from their joints and the scales which cover them, look catlike and endi in clawed paws.

Koibra reproduction in the wild is extremely rare, generally occuring during surges in magical energy at local leylines.  When natural reproduction does occur, Koibra form pairs which remain together to construct a nest, though they do not mate for life. Koibra lay clutches of eighteen eggs at a rate of two each day, one at midday and one at midnight. These eggs are buried to incubate in pairs in a nesting mound, similar to the nest mounds constructed by crocodilians. Female Koibra will remain to guard the nesting site until the eggs hatch and the hatchlings can hunt for themselves, after which point the young Koibra are left to their own devices.

Koibra who begin their lives naturally and not as the result of magical transmutations start as eggs which are roughly the same size as crocodilian eggs. The eggs incubate in a nesting mound until they hatch, after which point the hatchlings are protected by their mother for roughly the first three months of their lives until large enough to fend for themselves at around a foot long.    Hatchling Koibra are surprisingly vulnerable and skittish, but are active hunters. During this phase of their lives, they feed primarily on small reptiles, amphibians, insects, and fish, growing quickly and reaching roughly three feet long by the end of the first year of their lives. During this phase, their frills, fins, and hoods are also less developed and elaborate, and their colors slightly muted to help them better blend with their environment. Koibra continue to grow quickly, developing their striking coloration and pattern and their elaborate hoods and fins, until they reach a size of around ten feet long tip to tail- usually at around three years old. Although Koibra will continue to grow their entire lives, with particularly well-fed and old Koibra known to reach anywhere from fifteen to twenty feet long, their growth slows significantly after reaching adult size around their third year. Koibra are surprisingly long-lived, with some individuals in captivity reaching three centuries.

Koibra are rarely found in the wild, but small populations can form from escaped individuals. The inherent magic which produced Koibra makes them suspectible to rapid mutation, and they quickly mutuate to wild phenotypes if left to their own devices. Their cold-blooded, semi-aquatic nature means they are typically only found in the wild in warm-climates near bodies of water.    Koibra are capable swimmers, but prefer to spend their time immersed in still bodies of water like large ponds, calm rivers, or (in the case of saltwater Koibra) quiet lagoons.

Koibra are adept predators. As hatchlings they are voracious, and will attempt to eat anything they can catch, mainly small fish, amphibians, insects, and reptiles. At this age they actively patrol their environment, using their keen senses to detect hidden prey. As they age and grow, their hunting strategy evolves as they find themselves less agile and less proficient at catching nimble small fish and insects. At this point, Koibra focus their energy as ambush predators, using sudden strikes to inject prey with their powerful venom, leaving it paralyzed and an easy meal. This change in strategy also accompanies a change in the Koibra's preferred prey, as it shifts to larger meals which mainly consist of large fish, birds, mammals, but their favorite prey are crocodilians. As adults, Koibra can go weeks or even months between meals as they digest, and have very slow metabolisms.

Koibra are active year-round in the environments they normally inhabit, though as cold-blooded creatures their metabolism slows in cold weather. Unlike snakes, Koibra do not shed their skin, but rather lose scales individually. As unnatural creatures, Koibra do not have a natural mating season nor do they seem especially interested in seeking out mates. Mating can be triggered by surges in magical energy at local leylines, but generally, mating seems to occur between Koibra on an impromptu basis simply when two indivdiuals encounter one another.

Aside from those trained as guard-animals, Koibra are surprisingly docile and are generally uninterested in humanoids. When they are not hunting, they are largely inactive, preferring to sun themselves or lounge in the water, or glide lazily along the current with their wide fins and hoods flowing gracefully around them. When they hunt, they remain perfectly still in their chosen ambush-site, waiting for prey to pass before striking with their fangs to inject paralyzing venom and swallowing it whole. When they are smaller, Koibra are energetic and inquisitve, using their long barbels to sense hidden prey and their agile and flexible bodies to reach it in tight spaces and catch it. As adults, Koibra are territorial, defending their preferred hunting grounds and basking places, although if they are not separated from the rest of their clutch when they hatch, and are instead kept in close proximity to other Koibra throughout their lives, these socialized Koibra do not develop the same territorial tendencies and get on amiably with the rest of their clutch.

As normally solitary animals, Koibra do not have a distinct social structure. They are normally territorial, engaging in displays where they flare their hoods and fins to assert dominance over others, which can sometimes escalate to clawing and body-slams, although generally these displays end with the smaller individual retreating and finding a new territory. When Koibra of different genders encounter one another, they are as likely to view one another as potential rivals as they are to mate, and even after mating, Koibra tend not to remain in close proximinty to one another for long.    The only exception to this behavior occurs when clutches of Kobira hatchlings remain together as they age. In this circumstance, it seems Koibra do not develop their normal territorial instincts, and, where domesticated Koibra are kept together and food supplies are plentiful, Koibra can coexist peacefully with one another. This suggests that Koibra territoriality is more a result of practical limitations on the number of Koibra who can be supported by the local food supply, rather than any innate animosity towards one another.

Koibra domestication is an incredibly difficult, expensive, and time consuming project, but one which can yield immense rewards. Domesticated Koibra must be raised from hatchlings so that they imprint upon the domesticator, a challenging feat given anyone wishing to obtain Koibra hatchlings must first raid a nest and seize them from under the watchful gaze of their parent. Once they imprint on humanoids, Koibra can be trained to accept food and recognize certain indivduals as friendly, while their innate sense of territoriality means this energy can be easily redirected as a guard animal. Even when domesticated, Koibra are fickle and prefer limited contact with humanoids, mainly interested in them only insofar as they are sources of food and treats.

Koibra are most commonly kept as expensive but highly capable guard-animals for the highly-wealthy or magically inclined because of their ability to sense even those intruders obscured by magical means. Additionally, Koibra are sometimes kept as exotic pets and symbols of wealth, status, and prestige, with some noble families even keeping elaborate water-gardens and lily ponds to house them, selectively breeding them for their coloration and patterns. Additionally, Koibra venom is extremely potent, and can be distilled into a powerful poison and used to coat weapons, though it loses it potentcy quickly once exposed to air.

Koibra are found only in temperate and tropical regions

Koibra possess a limited, reptilian intelligence, capable of limited pattern recognition, instinctual cunning, and a limited ability to be trained, but lacking higher-order thought.

Koibra have impressive sensory abilities, both mundane and magical. While their vision is not especially good, they compensate for this ability with their tongue and barbels, with which they can "smell" minute chemical variations in their surroundings, allowing them to effectively "see" even in complete darkness, especially when combined with their ability to see on the ultraviolet and infrared spectrum. They are also highly attuned to electrical currents and pressure, giving them their own tremorsense and blindsight, while their barbels can also detect magical energy. This makes them adept at detecting magical currents and discerning through magical veneers and auras.