Just to clarify:
The cracks in time are the Time Lords trying to get back into the universe.
Madame Kovarian’s sect of the Papal Mainframe blew up the TARDIS to prevent him from reaching Trenzalore.
Silence Will Fall is the promise made by the non-Kovarian sect to not let the Doctor speak his name.
The Silents are the priests of the Papal Mainframe, and are genetically designed to make confessors forget once they’ve confessed.