Originally from Charos, Chuuls are large lobster-like creatures, which dwell in the Underdark.

Chuuls have been described as "a horrible mix of crustacean, insect, and serpent", but most closely resemble an 8 ft (2.4 m) brownish-green lobster weighing 650 lb (294.8 kg) with four long legs, two large claws, a strong protective exoskeleton, a fan-like tail, and a mass of tentacles around its mouth. Amphibious by nature, chuuls are actually not great swimmers, preferring to engage in combat either on land (where they could survive indefinitely) or very shallow water.

The tentacles that surround a Chuul's mouth are capable of causing paralysis with a single touch, thus leaving their unfortunate victims at the mercy of the chuul's powerful claws.

To attack, A chuul will wait by a shoreline, while submerged or partially submerged in murky water, until it hears a suitable prey, either within or without the water. Strong physical combatants, chuuls attack by grabbing and piercing their target with their enormous claws. After the unfortunate victim is trapped within the strong grip of a chuul's pincer, it is either simply crushed or brought towards the creature's mouth tentacles, which grasp the victim and exude a paralytic secretion. Even if the victim is able to resist the paralysis at first, they would eventually succumb, if not to the paralysis itself then to the creature's mandibles.

Much like a number of other creatures from the Far Realm, chuuls have limited psychic abilities. However, it is unusual for their young to have access to such powers, instead they gradually become able to exude limited psychic abilities as they age. Older and larger creatures are able to emit a psychic moan that weakens resistance to their psychic attacks and can use a psychic lure to draw victims towards them.

Chuuls are extremely alert, can fight in total darkness or even if blinded, and have an innate immunity to poison. Chuuls often associate with the Aboleth, serving as guards or soldiers in their armies.