Sirius Black

Double Strike, Trample
I don't know how I did it. I think the only reason I
never lost my mind is that I knew I was innocent.
That wasn't a happy thought, so the Dementors
couldn't suck it out of me... but it kept me sane and
knowing who I am... helped me keep my powers...
so when it all became... too much... I could transform
in my cell... become a dog.