Go to Asylum:Gateway and jump down onto the square pipe and turn left. Go past the flame buckets(with Gad Toucher) and eventually after passing some pig guards you should come across a room with alot of boxes stacked on one side and a cage with a Deadsider in it. Jump up the boxes and get to the top. Then jump onto the beam supporting the arch and do so again to the next and in the middle of the last one you should unlock play as Deadsider! Then go out through the other side and some Dark Souls lie in wait for you.