There was no way to apparate into Azkaban, Lily had made sure of that with a number of enchantments on the cold and lonely island. There were only a handful of portkeys that could teleport a person into Azkaban; these were shrouded in secrecy so only Haldor and himself could travel there. Fortunately, one of these portkeys was inside the castle itself. It was in the room of requirement, hidden amongst a hall of broken pots and debris, there was a pristine black pot, which, when touched, would suck you into an abyss, only to reappear at the ominous gates of Azkaban.