Visian

Visians are a semi-sapient species of invisible predators which inhabit the swamps of planet Mira, in the Milky Way Galaxy.

Biology
Visians are naturally invisible, but fully corporeal creatures and leave clawed footprints on the soil as they stride. From examining these footprints, the Doctor has concluded that they're about 7 ft tall (~ 2.13 m) bipeds.

When covered in wet mud, the outline of a Visian becomes visible, revealing that they're thin, skeletal creatures with a couple of long arms equipped with claws, and a narrow head with a beak.

Culture and society
Visians are cautious creatures, preferring to rely on their invisibility to overpower opponents. They become braver when in groups, and especially when they have time to plan out a strategy before they attack. They live in tribes ruled by a leader, but don't seem to have any form of technology, short of throwing stones at opponents. They generally speak in quiet whispers, so as to minimize the chance of being located by either prey or rivals.

Appearances

 * Doctor Who, season 3, "The Daleks' Master Plan" (1965)