Dolores umbridge the defense against the dark arts professor in harry 's fifth year , refuses to reach her students defensive magic . with e threat of voldermort looming over them , Hermione recruits harry to privately teach any interested students . meeting in the room of requirement , the underground resistance movement calls themselves ' dumbledore's army.

Expelliarmus : the disarming spell is very essential to any wand battle - it literally forces the wand out of the opponent's hand.

Stupefy : the stunning spell knocks out the caster's opponent , causing them to become semi or totally unconscious.

Reducto : the reductor curse reduces the target to pieces . Ginny uses it to destroy the practice opponent in the room of requirement and again in the hall of prophecy.