Bloodstained: Ritual of the Night/Techniques

Techniques are special attacks that Miriam can perform with a specific set of weapons and a command input. There are bookshelves in the castle that add journal entries with the details of a technique, but they are not required to unlock the technique. You only need to have one of the listed weapons equipped when you input the command. Using a technique on an enemy will progress its mastery gauge. Once it is mastered, any weapon of the same type can be used to perform the technique.