The belabra were distinguished by a hemispherical shell that was roughly 2 ft (60 cm) in diameter. The shell was black or dark gray in appearance. The belabra's barbed tentacles extended from the underside of the shell. They had 12 tentacles in total. Under the shell, it also had a gray beak and a white underbelly. Four eyes extended above the shell on short eye stalks.
A belabra used its shell as a shield, and would constantly move to position itself in a defensive posture. When it attacked, it would either lunge at its target and use its shell as a ram, or would entangle the target with its tentacles and then use its sharp beak to tear flesh. When it lunged, it could glide up to 60 yards (55 m).
If injured, the belabra's gray-white blood acted as a poison. It could cause partial blindness or constant sneezing upon contact.
The belabra, when at rest, retreated into its shell and remained still. It was often mistaken for a boulder or large rock when it was resting. It used its sense of sight and smell to hunt.
They only had one sex, although they were not asexual, as two belabra were needed to reproduce. The young began as buds on the inner wall of the parent's stomach. Gestation lasted from six to ten months. After gestation, the young were ejected.
Many sages believed that the belabra were primitive versions and evolutionary precursors of the flumphs and grells, due to a few shared characteristics, such as the debilitating effect of their toxic blood and their mode of reproduction.
If a belabra was captured at a young enough age, it might be domesticated. It could be trained to obey simple commands and could be used as a guard or a hunter. A trained belabra could capture and hold prey without killing. It formed a bond with its trainer, and could distinguish them from prey during combat. Training took a number of weeks and only a skilled instructor should make the attempt. A captured belabra could fetch 1,500 gold pieces at a market.