Doctor Who: EVERY NuWho Villain And Monster Ranked Worst To Best

Appear in: Knock Knock.

These creepy-crawlies were found by a boy called John in his garden, who then showed them to his dying mother Eliza. But being extraterrestrial insects, they possessed an astonishing ability to keep Eliza alive - more like preserved, as her whole body turned into wood.

While under the control of John (the Landlord, played by David Suchet) the Dryads were used over a 70-year period, up until 2017, to harvest young people's energy and matter for Eliza to absorb. They did this by ensnaring victims into the wooden walls of the house where John and Eliza resided, then disintegrated them into complete nothingness.