"Well, you could say that we are old friends. The Doctor and I have known each other for a very very long time. Too long, perhaps."
The Master raised his eyebrow at the letter comment. "Sent him a letter? As amusing as that might be, you misunderstand me. See, sending him a letter would work if I wanted his help. I don't. I want him out of the way. There is no easier way of doing that than taking his daughter and telling him to work on the rift instead. He will ignore me completely and come searching for you. That will leave me free to find out who or what is doing this." And inquisitive expression crossed his face.
"Tell me, do you know what happens when too much matter and gravity gathers in one place? The result is a black hole. Well, this rift is taking time and dimensions and throwing them all in one place. Do you really want to find out what that will cause?"