D is for... Drashigs

Huge reptilian creatures with snake-like bodies, from one of the satellites of the planet Grundle. They lived and hunted in the marshes. They were of voracious appetite and were omnivorous. When a battle-cruiser crash-landed on the moon, it was said that the creatures killed all 50 crew and ate their spaceship, save for a few engine parts. The Doctor and Jo Grant encountered a colony of the beasts whilst trapped inside a Miniscope device. This was a form of intergalactic peep-show, which had been taken to the planet Inter Minor by a couple of entertainers - Vorg and Shirna. The Doctor and Jo broke out of one exhibit and found themselves inside the machine's workings. They then broke into the Drashig exhibit. The Doctor used his sonic screwdriver to ignite marsh gas, allowing them to escape. However, once they get a scent the Drashigs never relent in their pursuit of their prey. They broke out of their exhibit into the workings, and then invaded the other exhibit which the Doctor and Jo had visited - the ship SS Bernice. The crew killed a couple of them, but soon the Drashigs managed to get outside the device, with the assistance of a devious Inter Minoran Official - growing to their full size. Vorg used a laser cannon to despatch them.
Jo was particularly traumatised by the creatures. When subjected to the Master's hypnotic fear-inducing machine she saw an Ogron as a Drashig, and later the Master himself appeared to her as one of them.
Later, the Doctor gave the stage magician Professor Clegg his sonic screwdriver, to see what images it brought to his mind. He saw the Doctor use the device against the Drashigs in the Miniscope.
Memories of the creatures were used by the Shansheeth to make Jo help materialise a replacement TARDIS key.

Appearances: Carnival of Monsters (1973).
Cameos in Frontier in Space (1973), Planet of the Spiders (1974), SJA 4.3 Death of the Doctor (2010).

• Drashig is an anagram of dish-rag, as writer Robert Holmes feared his creatures might be realised by such.