The Emphani
From Tardis Wiki, the free Doctor Who reference
The Emphani was a parasite that could inhabit bodies through the phrase "I love you".
Its way of surviving was using somebody's body as a host, destroying all of the person's memories of anyone else. Charlie Smith and Matteusz Andrzejewski were alone in the Coal Hill locker room when the Emphani came through the rift. Its first victim was Matteusz. (AUDIO: Tell Me You Love Me).