Dryad

Lice, or "Dryads" - as coined by the Twelfth Doctor, were insect-like creatures which lived in wood and fed on humans. They lived in a house owned by the Landlord after he found three individuals outside, which had some healing properties that saved Eliza, however turning her partially into wood. In order to properly heal someone however, they had to be regularly fed people, so the Landlord decided to make the house cheap to lure people into buying it. He'd also use a tuning fork to call them to the area where the inhabitants were.

In the end, Eliza controlled all the Dryads into eating her and her son in order to stop the killing that was keeping her alive, and as a result all the Dryads left. (TV: Knock Knock)