Someone at Ubisoft decided that Assassin's Creed needed more tower defense. This person was very, very wrong. Look, all I want is to stab some throats and scale some towers when I'm playing Assassin's Creed: Revelations. You don't need to muddy the experience with annoying side missions built around entirely different genres. Besides, the whole scenario doesn't seem to fit a group of assassins. I can only imagine how Ezio's subordinates feel about the situation.