O principal exemplo é o uso de feitiços não verbais. Snape ensina os sextos anos de habilidades não verbais. Alguns dos feitiços de proteção usados, Harry ensinou no DA, mas Harry não ensinou ao DA como executá-los não-verbalmente.
‘... you are, I believe, complete novices in the use of nonverbal spells. What is the advantage of a non-verbal spell?’
Hermione’s hand shot into the air. Snape took his time looking around at everybody else, making sure he had no choice, before saying curtly, ‘Very well – Miss Granger?’
‘Your adversary has no warning about what kind of magic you’re about to perform,’ said Hermione, ‘which gives you a split-second advantage.’
Half-Blood Prince - page 170 - Bloomsbury - chapter 9, The Half-Blood Prince