In the Dungeons & Dragons game, a belker's body is composed primarily of smoke, ash and grit. It is bean shaped, with a wisp of steam for a tail, demonic looking bat's wings, red eyes, and two smoggy arms with claws.
Though belkers in the game are undeniably evil, they are reclusive and have very little interest in the affairs of others. If angered, however, it attacks without mercy. Sometimes, it attacks with its teeth and claws, and can blind opponents with its stinging ash, but there is another way. If a person inhales a belker, it solidifies and tears them apart from the inside. Coughing one back up is the only way to escape this horrible death. Most of the time the belker has a solid form, but it can assume a smoke form at a whim, allowing it to be inhaled for the inside attack, and to fly more easily.