An Ankheg resembles an enormous, eight-legged insect, with a thick-armored carapace like that of a lobster. It has six spindly spined rear legs connected to its abdomen, and a pair of powerful forelimbs modified into powerful mantis-like graspers with thick spikes. Its head is armored and torpedo shaped with armored flares and long twitching attenae, and a pair of crushing mandibles capable of snapping even small trees in half.

Ankhegs may lay up to a dozen eggs in a clutch, typically producing eggs once every other year, typically in off years from a moult. A female Ankheg mates with as many males as possible, who display no paternal instincts and may even prey upon their offspring. On the other hand, female Ankhegs display strong maternal instincts, not only digging a nest for her young, but bringing them fresh kills for their first month after they hatch until their first moult. After the young experience their first moult and their chitin hardins, they dig their own way out of the nest and begin to forage for themselves and live independently, while their mother moves onto new territory.

From once Ankhegs hatch, they appear as miniature adults, roughly the size of small dogs, not experiencing any pupal or subadult stage. After their first month of life, they grow rapidly, moulting for the first time and emerging as the size of a mastiff. Over the next seven years, the young Ankheg will hunt and grow, moulting annually until they reach adulthood.   After reaching their adult size, and becoming near apex-predators, an Ankheg's metabolism slows dramatically. At that point, their moults take place only every other year, while in off-years female Ankhegs seek out mates, and male Ankhegs battle for territory.

Ankhegs can be found worldwide, but they prefer areas with a layer of soft topsoil over packed earth, clay, or soft rock, which is most suitable for their hunting style and burrowing, although they can burrow through solid stone itself if given time and sufficient inclination. Oftentimes, this preference for soft soil tends to overlap with fertile farmlands or rich forests. An Ankheg's territory will rapidly become crisscrossed with a network of tunnels, allowing the Ankheg to quickly traverse from preferred ambush site to ambush site. Tunnels are usually dug far enough below the surface to avoid risks of cave-ins or unintentional discovery, but close enough to allow the Ankheg to sense occurences on the surface and lie in wait for prey. Ankhegs can quickly depopulate an area of large prey, and as a result, they are often forced to become less selective in their targets or move on to new territory quickly. However, places with a large concentration of prey, or where prey are quickly replenished can become favorite targets for Ankhegs, often resulting in Ankheg's being drawn towards pastureland.

Although Ankhegs receive a certain portion of their nutrients from the organic matter they consume as part of their burrowing, they must supplement their diet with fresh meat. Pastures teeming with grazing livestock and forests rife with game are an Ankheg's prime hunting grounds, making Ankhegs the bane of farmers and game wardens everywhere. An Ankheg's preferred prey items include typical large game like deer, elk, boar, and aurochs, domesticated animals like cattle, sheep, and horses, or even large predatory species like bears, great cats, axe beaks, or large reptiles. In lean times, Ankhegs have even been known to hunt smaller prey items like wolves, and, most concerningly, humanoids.   An Ankheg is an ambush predator, lying in wait underground and springing out in a rapid attack. During this attack it stuns and grapples prey with strikes from its massive forelimbs before dispatching it with a devasting, acid-laced bite (actually the Ankheg's blood!) from its mandibles before quickly retreating underground with its catch to feed in peace.

During winter, Ankheg withdraw underground and enter a state of semi-torpor where they remain active enough to defend themselves and may slowly expand their warrens, but do not hunt. This may also be a result of snow disrupting the Ankheg's normal termorsense.   However, Ankheg who live in tropical climates, or populations in the underdark who exist entirely subterraneanly, do not display this season lull in activity.

An Ankheg uses its powerful mandibles to dig winding tunnels deep beneath the ground. When it hunts, an Ankheg burrows upward, waiting below the surface until its antennae detect movement from above. Then it bursts from the earth and seizes its prey in its mandibles, crushing and grinding while it secretes acidic digestive enzymes. Ankheg's prefer prey that is isolated, though its presence in a group will not typically dissuade an attack, as an Ankheg assumes they will simply scatter in fear at its strike and leave it to feed. If attacked or threatened, an Ankheg will simply retreat back into its warren, relying on the network of tunnels to confuse any pursuers, and lashing out in vicious strikes or with acidic defenses if cornered.

Ankhegs do not have any known social structure, and in fact are generally hostile and even cannibalistic if they meet each other. Ankheg young have been known to consume weaker siblings or unhatched eggs in their first month before leaving the nest. An Ankheg of significantly smaller size than another it encounters is likely to end up as its meal, while similarly sized Ankhegs view each other as rivals and threats to an already perilously short food supply who must be driven off. Female Ankhegs wander endlessly, seeking out new prey and mates, while male Ankhegs seek to establish prey-rich territories in the hopes of attracting females. Still, males must be careful to only approach females of similar size who welcome their advances, otherwise such liasions are likely to end not with mating but with combat and/or cannibalism. To best secure their chance at breeding, male Ankhegs approach females with a sufficient offering of fresh-caught prey, ideally distracting the female long enough to mate and be away. Aside from these encounters, Ankheg are totally solitary.

Although many have tried to domesticate Ankhegs, their low intelligence has rendered them utterly incapable of domestication. Even young Ankheg may be corralled and tightly controlled for as long as possible to physically dominate it, but their general independence from birth, powerful builds, and predatory instincts make them inherently dangerous, and an adult Ankheg is utterly unmanageable. While tales of empathetic adventurers raising orphaned Ankheg young or hatching eggs in an attempt to domesticate them do exist, such stories rarely end happily, ending at best with the Ankheg released to the fringes of civilization to live out its days far away from anyone it could threaten or who would kill it, and at worst with lost limbs or lives. Still, the foolhardy do occasionally try to domesticate Ankhegs (or to at least point their destructive energy in a specific direction), generally to catastrophic results.

An Ankheg's chitin is extremely hard, and is an effective, if sometimes even superior, substitute for iron or steel armor. As a result, it is highly sought after to be repurposed into armor, especially by those who lack the means to work metal. Additionally, certain tribal groups seek out Ankheg armor as a symbol of a warrior's personal prestige and combat prowess. An Ankheg's large and distinctive headplate can make a particularly imposing helm, while plates of chitin may be fastened as armor plates and the forelimbs can serve as spike gauntlets or pauldrons.   Additionally, an Ankheg's acid is highly potent, capable even of dissolving stone, though it has little effect on glass. It is occassionally collected for use in alchemy, construction, or as a unique weapon.   Finally, while an Ankheg's meat is usually inedible due to its acidic blood, the blood and meat together can be fermented in alcohol (a dwarven discovery) to make a hard liquor known as Ankheg Spit, whose taste is similar to that of tequila but much harsher and far more potent.

An Ankheg's head is long and torpedo shaped, with broad spiky chitinous plates flaring out from the sides and protecting a pair of small, beady eyes and the Ankheg's mouth parts. The Ankheg's blade-like mandibles are almost the same length as the head itself, typically two to three feet long and six to ten inches wide, while long antennae protrude from around its face and mouth.

Ankhegs can be found worldwide, but they prefer prey-dense areas like forests and pastureland, while also being found deep in the underdark.

Ankhegs are extemely dimwitted, responding to stimuli and instinct alone. They are not capable of any sort of long-term thinking or planning nor do they have any self-awareness.

An Ankheg's vision is poor, but its spined legs and long attenae keep it well attuned to any subtle tremors or movements around it, and it is capable of sensing even slight variations in pressure on the ground out to sixty feet away.