"Correct. Take ten points. Just being in the same surroundings helped to fill the gaps. Another reason? Mr. Malfoy?"
                              
Draco hadn't read ahead, but he understood Memory Charms. "Because you didn't use a lot of force in your spell?"
                              
"Good. Ten to Slytherin. As one uses a Memory Charm, they have to decide the amount of pressure on the block. The more power you use, the less likely they will remember. However, using high-level charms will result in permanent brain damage and noticeable disorientation. It would make the memory augmentation known, obvious, and therefore, the potential for others to repair it. If you know the signs, you will know that a Memory Charm was used. The main purpose for using such a charm is to escape notice. Whether using it legitimately as a Ministry-approved reason or illegally, to hide illicit activity. Using memory charms, in that sense, is, of course, highly punishable under the law and would result in a lengthily prison sentence.
                              
"But the subtler the erasure, the less likely that residual signs will remain and the more difficult to know that there is a lost memory to recover. However, it will be easier to recover a memory that only employs a weaker spell. Now, Ms. Granger stated that just being where the memory was taken helped, but what if you don't know where or when a memory was taken? Who was here? Or why? That's why we need to know the signs that a Memory Charm was used and why employing a heavy spell, that shows more obvious signs that a memory augmentation occurred, is so imprudent.
                              
"So, when you employ a Memory Charm, it is better to use a less powerful spell, even when it comes to protecting the International Statute of Secrecy. If the muggle remembers bits of what happened, they will most likely think it was a dream or their imagination. However, the more traumatizing the event, the more force will be needed and the side effects will be obvious and dangerous. If it is too powerful, the mind may never recover properly either."
                              
Draco nodded. He heard Lockhart never did get his memory back.
                              
"There was one other reason why Dean got some his memory back quite easily... does anyone know?"
                              
Hermione again had her hand up, but the professor picked Harry, who bit his lip considering it. "He was afraid."
                              
"Another ten to Gryffindor. Fear... fear drives your memories and emotions more than anything else, especially the fear of pain. People remember fear. It leaves the most lasting memories... even more than the actual pain does, and it is harder to forget it, or erase it. If the memory was one of intense fear or pain, a powerful spell will be required, though I do not advise ever putting more force into a Memory Charm, if you are inexperienced. The Ministry has trained Obliviators for a reason. Even after a stronger spell is used, there will still be remnants, like a sort of déjà vu. Little things that they will remember, even if they couldn't remember why."
                              
"Now, there are several ways to detect Memory Charms, aside from the signs, but the spell is difficult to use, the longer time has passed," Flitwick went on, showing the class how to magically detect Memory Charms and they took notes as he spoke and went over the correct wand movements and pronunciation.
                              
Dean hated all the attention on him. Draco, however, caught Flitwick giving him a wink, and knew he was targeting Dean for a reason. Draco gave a low chuckle under his breath, again. He glanced to Blaise, took advantage of their non-break and put his hand on Blaise's arm: a request for information.
                              
"I'm okay... honest. I'm better," Blaise whispered, but his confidence was shattered. He glanced longingly at Neville, who was openly sleeping on the other side of the room.
                              
"You don't look it," Draco muttered.
                              
"Had something things to work out. Thank you... for last night," he murmured quietly.