Cross walked to McGonagall's office. He could have just teleported inside, but he felt that would be rude, so he walked.
Cross entered the room and looked around, it looked the same as before. Cross smiled and said hello to the hat, who responded "Ahh, Cross. Nice to see you again." Cross grinned and said "Hasn't been too long has it?" the hat chuckled and didn't say anything.
McGonagall had a serious face as she said "Mr. Greengrass. I have heard about your methods!" Cross sat down and said "What do you mean, Professor?" McGonagall said angrily "Killing a Death Eater in front of a class of 6th years!? Have you gone mad!?"
Cross pretended to not know as he said "Death Eater?" McGonagall continued "The man from your trunk, the one you said you caught outside, the one you have Ginny Weasley use the Cruciatus curse on."
Cross had a look of realization as he said "Ohhhh! No, you see he was dead when I found him, thus wasn't alive the entire time." McGonagall felt her eyes twitch as she said "And when he spoke?" Cross looked around the room and licked his lips as he grinned "You see, somethings dead people speak. Very strange phenomena if I might add! Post-Mortem Exposition is what I call it, haha..."
McGonagall leaned back and rubbed her eyes, taking off her glasses in the process, before saying "Cross, I can't have you scarring the students." Cross gave up at the facade and said honestly "Pressor, you know as well as I do that this year will be far from peaceful. The 6th and 7th years will be fighting Voldemort's army, if they cannot handle a single death, not in their own hands, then they will not survive till the end of the year."
McGonagall sighed again and Cross continued "I understand that perhaps my methods are a bit extreme but this, I find, is necessary considering the crisis. He's not the headmaster anymore. His bullshit 'peaceful endings' will not suffice against Wizards who have the intent to kill. Pardon me for being rude, but if these kids stay the way they are now, I estimate over half will die with the first and second years being completely eradicated!"
McGonagall seemed to have aged by 10 years and Cross shook his head as he said "They need to be ready to fight and kill-" McGonagall interrupted "You're training an army!" Cross retorted "If that's what it takes then fine, because if not, they will die! You can see this too! Voldemort might be retarded but there's a lot more retards under him..."
Cross looked at McGonagall and said seriously "Me, you, a few teachers, the beasts from the Forbidden forest, and a few others can fight but do you have the confidence to kill them all and protect the students at the same time?"
McGonagall was silent and Cross smiled "Professor, let me tell you something. If something unexpected happens, I will flee." McGonagall was shocked and looked at Cross incredulously as she said "You-" Cross cut her off and said "I haven't gotten married yet and I will not leave my unborn child without a father."
McGonagall choked her words back and looked at Cross with a heavy sigh, understanding what he's trying to say. Cross added "I will not protect the students by sacrificing my own life, not only is my life more precious, but who are they to be worthy of this King's sacrifice?"
McGonagall rolled her eyes as a small smile escaped her lips and she said "Yes, well. 'Your Highness', if you could just not literally kill people in class that would be much appreciated." Cross smiled and said with a chuckle "I only had one Death Eater anyway~" before teleporting as McGonagall threw a book at him.
She smiled and looked where he just disappeared from before sighing and closing her eyes mumbling "I hope that they will be ready..."
The next day
Cross continued teaching his DADA class, the younger kids got a fun demonstration with Cross' clone acting like he was attacked and that the actual Cross was an imposter. The kids were were scared before Cross showed them that it was in fact a clone, then they laughed and cheered, thinking that Cross was the best teacher in the entire world.
It was true.
The 7th years got a full presentation on all three curses and Cross went above and beyond what happened last time before telling them that they were in fact the front lines against Voldemort's moron army and that they had to keep it a secret from the other teachers.
He killed another Death Eater in cold blood in front of them as he said "They will not show mercy to you, in fact, I managed to hear that whoever kills the most students will be rewarded from Voldemort himself." that lit a fire under the students and they started actually practicing frantically.
Days passed by
During which Cross taught Ginny personally while Luna was resting, he was training her to be a real machine.
His classes with the younger kids got him praised from McGonagall while she turned a blind eye to the older students. Cross had decided to take it a step further, he gathered all the 6th years and 7th years and brought them into the Room of Requirement.
The Room expanded to fit them all and Cross stood in front of them as he said "Welcome to Fight Club. Now in this 'Fight Club' I will be thoroughly training you all in the Unforgivable Curses, harmful spells, Defensive spells, charms, hexes, jinxes, and how to turn a common spell into a ruthless blood seeking weapon. Any questions?"
Neville asked "Is it true? Are you gonna have to fight?" the rest of the students were curious and nervous as well, Cross smiled, but in the students eyes it was a predatory smile, truly chilling, as Cross said "Of course! You think that moron won't attack the school that he hates more than anything in the world?"
The students were silent and Cross grinned as he added "I can see that you're all thinking 'I can't believe this!' well truthfully, I couldn't care less what you believe or not. Hehe. Leave the school and ruin your futures if you like, hell, don't come to my lessons anymore! If you die, it actually doesn't affect ME in any way, shape, or form if you can believe that."
Cross chuckled and said "Actually, I won't even lose sleep over your deaths. You're not the special snowflakes your parents make you out to be and I'm not a saint, hell, I'm not even a good person..." The students' face turned ugly but Cross shouted "HOWEVER!"
The students looked at Cross, a bit startled by the change in tone.
Cross continued with a smile "If you want to protect the school which gave you everything you currently have! The friends you've made! The memories you share! If you want eternal glory! Pride! If you want to be regarded as a hero, who stepped up in a time of peril against one of the Darkest Wizards in history! Able to tell your families for generations about how you didn't run, you didn't hide, you stepped forward and defended those took weak to fight behind you, casting your tall shadows on their small backs as HEROES! Then, perhaps you should stay~"
The students felt their blood pumping, as their fear slowly diminished. Luna was looking at Cross in a daze, biting her lips with intense love in her eyes. This was her man! Astoria was jumping up and down in excitement, Daphne had a calm smile on her face, while Ginny had an excited grin.
Cross shouted "What's it gonna be! Are you going to run like a bunch of pussies?! Or are you going to be Heroes!" The students said "Heroes." Cross shouted "I can't hear you!" the students shouted "HEROES!"
Cross grinned and said "Good. First rule about 'Fight Club'..." Cross kicked a chest next to him, dozens of tied up Death Eaters fell out as Cross finished "Don't talk about Fight Club."
No kidding. He was basically training an army, if McGonagall heard, he would get fired maybe five minutes later.
Seemed like his speech worked though, as none of the students ratted him out and listened to his training very seriously. Cross taught them everything he knew about fighting and more importantly, how to be ruthless. Not only with Unforgivable spells but the old ones like Lumin Spear, and a few others, it was actually very fun for him to teach these kids how to fight.
Maybe he had a future in teaching?
Regardless of whether he was a good teacher or not, he made them do daily exercise in the mornings. A nice run around the School grounds, while he floated in front of them on a broom with Luna, occasionally creating obstacles and throwing green spells at them.
These kids were terrified from the green spells and jumped out of the way in fear for their lives. Obviously it didn't help that Cross would shout 'Avada Kadavra' whenever he threw a green spell. Cross was proud to say that they all dodged and not a single one of them was hit.
One of the students once complained that Luna never ran and Cross replied "When you become pregnant, you won't have to run either." the male student turned green and kept running, while the rest were shocked but still ran as a debatably real Avada Kadavra flew over their heads.
Obviously, Cross didn't actually throw Killing Curses at them, but they didn't have to know that did they? They dodged for their lives in true fear of being killed by this madman. As time went on, Cross earned the title 'Mad Elf', with good reason.
He had hit a student with one of his fake Avada Kadavra spells. It was Neville. The situation was like this.
Neville collapsed to the ground on his back and didn't move anymore, the rest of the kids stopped in terror and Cross said evilly "Longbottom couldn't make the cut. How many of you will survive till the end?" as he licked his lips and his fingers glowed green.
The students bolted as fast as they could in pure terror, and made explosive improvement. Some even used wandless and wordless magic to speed themselves up, Cross was happy at their progress, it had been a few months since he started the training.
He flew over to Neville and slapped him awake, before throwing him in his beast bag. Luna went inside to reassure Neville, who most likely thought he was now a ghost, as Cross chased the rest throwing more 'Avada Kadavras' at them.
To his surprise they were quite the nimble group after the incident with Neville.
A few days later
Some of the students saw Neville was back and almost fainted from fear, thinking that they saw a ghost. Cross had the funny idea to dress Neville up as a Japanese ghost, white robes and triangle headband and all.
He actually had to get Neville to work with him a bit, so that the others would work harder due to fear. Neville would start spouting bullshit about how beautiful the afterlife was and the color drained from the other student's faces as they ran for their lives as Cross chased them.
Neville joined them, working as hard as he could, while retelling his stories of the afterlife. As more students got hit and 'died' Cross started dressing them up too and soon there was a 'ghost' group walking around the school, spooking the younger students and confusing the ghosts.
Cross had to go drag some students out of their beds to practice once and he said that they would sleep forever if they missed another practice meet, in the morning or in the Room of Requirement.
There was never another absence again.