To save Nevil from the ghoul you have to do a series of tasks and then shine lumos duo into the ghouls eyes and then shine the light on him untill he reaches the special roo that you lock him in and then Nevil will jump down and you must return to the Boy's dormitory.

to save him first switch to ron then go to the big blue box press a then it will pop up then you need to aim at all the toy s then go in the room then go up to the book learn the light spell then ghosts will appear shine your light on them then when it wears out quickly use flipenedo on it [do it a number of times then more will appear } then shine the light on the ball then move the mirror so it shines on the eye then go through the room kill more toys then a little missile robot will come then when the missiles shoot at you move but shoot flipendo at it jump down to harry now go up to yhe ghoul now go infront of it and cast the light spell and push it into th3e room that ron found with the spell note when you get down there will be a special room that only ron can open then sometime neville will come down then go back to the common room.seeya