Inimicus didactylus was first formally described as Scorpaena didactyla in 1769 by the German naturalist Peter Simon Pallas, with the type locality given as the Indian Ocean, thought to be Indonesia.

The skin is without scales except along the lateral line, and is covered with venomous spines and wartlike glands which give it a knobby appearance.

It is nocturnal and typically lies partially buried on the sea floor or on a coral head during the day, covering itself with sand and other debris to further camouflage itself.

When disturbed by a scuba diver or a potential predator, it fans out its brilliantly colored pectoral and caudal fins as a warning.

When it does move, it displays an unusual mechanism of subcarangiform locomotion — it crawls slowly along the seabed, employing the four lower rays (two on each side) of its pectoral fins as legs.