Solution: PH6: Time Frame

Answer: GRIM

The pieces fit together as follows:

Letters spell: THIS VOLUMINOUS UNHOLY DOG HAUNTS CHURCHYARDS

The Time Turner is first seen in Harry Potter and the Prisoner of Azkaban. In that same book Professor Trelawney says, “The Grim, my dear, the Grim!...The giant, spectral dog that haunts churchyards!” So the answer is GRIM.