The Silence
From Tardis Wiki, the free Doctor Who reference
The Voice describes an unknown, but powerful enemy who forced the TARDIS to explode, and thus created the cracks that would erase the Universe. (DW:The Pandorica Opens/The Big Bang)
Although the entity behind the voice is never seen or named, it is heard speaking before the TARDIS explodes, saying: "Silence will fall." (DW: The Pandorica Opens)
