It was those damnable stories - the Raggedy Doctor stories she'd traded her "Rose and Jack" stories for when she'd been out of their sphere of influence. Not much they could do about that.
It was also her mother, the notorious Amy Pond. She was too entwined with history, though - too entwined with the Doctor's history. They tried to end her, once - sent an auton with her fiance's face at her - but somehow it had gained her fiance's soul and went through hell and high water to bring her back.
And her father. Rory. He was an influence, and after her conception he could be safely removed without much damage to the timeline; anything he accomplished was mostly Amy, anyway. Yes, he could, and should, be erased.
And then they tried.
Time after time, they tried to kill Rory - shooting at him, burning him alive, poison - but he escaped, again and again, sometimes injured but never unsalvageable. Their guns would jam. Their poisons would miraculously become inert. And then they saw the writing on the wall.
Bad Wolf.
Oh, they knew of Bad Wolf. Anyone who had studied the Doctor's ninth or tenth incarnations knew of Bad Wolf most intimately, and the others all saw shadows - scarcer, but undoubtedly there.
Bad Wolf had taken an interest in Rory, for some reason. And for the moment, that meant he was untouchable.
"Perhaps we're going about this the wrong way," said Madam Kovorian, dead only for a forgotten moment in a forgotten timeline. "Perhaps we ought to go straight to the source. After all, we can certainly find a use for Rose Tyler."