Pius Thicknesse is first introduced in "Harry Potter and the Deathly Hallows". He is the Head of the Department of Magical Law Enforcement at the start of the book, when he is placed under the Imperius Curse by Corban Yaxley, who uses his position to infiltrate the senior ranks of the Ministry. Thicknesse is described as a man with long hair and a beard, which are mostly black but tinged with some grey, along with a great overhanging forehead and glinting eyes. Harry's immediate impression is of "a crab looking out from beneath a rock."