I think that Bok the gargoyle is one of the great Doctor Who monsters of his day. He makes a tremendously horrifying first appearance at the end of part two of this story. Our kid was behind the sofa like a rocket and he’s grousing that this is not a good story, because it’s far too scary.
But with fear comes imagination. He’s let us know that since gargoyles are made from stone, then the Doctor will have to use a rock hammer against the menace. “And those weigh 20,000 pounds!”