Graske (The Pest of Paternoster Row)
From Tardis Wiki, the free Doctor Who reference
A Graske once tormented the Paternoster Gang by infiltrating 13 Paternoster Row. It was able to hide within the walls, and even landed a bite on Strax's leg. It replaced Jenny Flint and had sent her to limbo, but when threatened by Strax and Vastra eventually causing it to vanish and returned Jenny back to Earth. (PROSE: The Pest of Paternoster Row)