I've been replaying DAO and I have to admit it's kinda hilarious how each class' 'evil' specialization is obtained.
For blood magic, one must sell the soul of an innocent child to a demon.
For the reaver specialization, one must defile a sacred artifact for a crazed cultist and drink dragon blood.
For an assassin, one must be nice enough to Zevran that he's willing to show you. Zevran has morals.
One of these is not like the others.