Harry trudged to his next ABO class with the very embodiment of loathing in his eyes. 

"You're making the whole hallway stink of your pheromones, Potter," Zabini spoke from behind him, coughing lightly. "Stop being so pissed."

"Fuck off," Harry snapped.

"Zabini, darling, be more kind, he can't help it," Pansy sighed, saddling up next to Harry, her heels clicking against the stone floors. "How are you feeling? Any better?"

"I'm fine," Harry grit out, keeping his stare on the floor. Left foot, right foot, left, right, left, right...

"Stop being a busy-body, Pansy" A third voice chimed in. Malfoy. Harry lost track of which foot he was stepping with and stumbled. 

A delicate hand grabbed his arm and steadied him- he could tell without looking that it wasn't Malfoy, which was a relief. However, it was still Pansy, which wasn't much of an improvement. 

"Easy, doll."

"Don't call me that," Harry grumbled, yanking his arm from her grasp. He was surrounded by Slytherins- Zabini behind him, Pansy to his right and Malfoy to his left. He felt suffocated. 

"You can try to get her to stop, but she won't. She comes up with the worst nicknames." Malfoy huffed under his breath while Pansy chuckled. 

"What's wrong, Drakey? Don't like my names for you?"

Harry snickered, despite himself. Pansy grinned villainously. "I have worse, Potter, I just figured I'd save him the embarrassment. I'll tell you later, if you so please."

"Pansy," Draco warned, but she merely laughed again.

Thankfully, they got to the classroom, sparing Harry from being trapped in the group of Slytherins. Luna was already there, and he took the seat next to her graciously. 

"Hullo Harry," she greeted lucidly, smiling.

"Hi Luna," he mumbled, dropping his bag to the floor and sneaking a look over at the table of Alphas before Lauralee cleared her throat and he dragged his attention back to the front.

"Alright. Since Harry is back-" Harry flushed a deep red color. "I can begin teaching you about the differences your bodies have gone through, being a bit different from the Betas. First, scent glands." Lauralee flicked her wand at the board in the front of the room, showing a diagram of a neck. 

"For both Alphas and Omegas, the scent gland is here, on both sides of the neck, right where the neck fades into the shoulder." She tapped her wand against the outlined gland and Harry subconsciously brought his hand up to rub at it. He'd noticed they was slightly swollen during his heat but had assumed he's just injured it somehow. "It is where your pheromones come from, and also where claiming bites are made. I'll be handing out packets with more information later, but claiming bites are life-long bonding between an Alpha and Omega, whereas the alternative- scent marking- is much more temporary, typically lasting from only a few days up to a few weeks."

Harry watched as she flicked her wand again, this time showing... Well... Male anatomy. 

Everyone but Pansy looked awkward. She winked at Draco, who rolled his eyes and swatted her shoulder. 

"Male Alphas, pay attention." Harry watched, in horror, as the... anatomy... went through several slide-show style flips, showing the base of the prick swelling. Draco and Blaise's eyes widened, the Italian boy's hands reaching down to cup over his groin region protectively. 

"Uhm, Professor Lauralee?"

"Yes, Zabini?"

"Uhm... Ouch? Right?"

She frowned, the slideshow still flicking through the stages of swelling on loop behind her. "No, not 'ouch', Zabini. When you copulate with an omega, whether it be male or female, the base of your prick will expand inside of them to prevent semen from escaping and increase the chances of pregnancy."

Pansy started to cackle at Draco's horrified look, but she quieted down when Lauralee cleared her throat pointedly. 

"This process is painless and typically lasts from five minutes to an hour, depending on multiple different variables, including heats, ruts, and general fertility. I must warn you, do not, under any circumstances, attempt to pull out from them while you have a knot. You will severely damage the Omega."

Harry winced and Luna pat his back sympathetically.

"As for female Alphas, the only true changes are having slightly larger hips and busts, though the reason for this is unknown." Pansy smirked while Draco and Blaise rolled their eyes. 

After that, Lauralee gave out stapled packets of information (Harry took great amusement in the Slytherin trio's marvelment over simple muggle paper and staples) about scent marking and claiming.

Information: Scent glands are located at the crook of the neck and cover a large area just beneath the skin, allowing a specific combination of pheromones to be released. For example, an unmated Omega may release pheromones encouraging Alphas to approach, whereas an Alpha may use them to warn other Alphas to stay away. Strong emotions typically cause bursts of pheromones to release in both secondary genders, intentional or not, and both genders can be equally impacted by them, though it is reported that Omegas tend to be much more susceptible to emotions released by Alphas than any other combination. Alphas can also react in a highly volatile manner, however, to Omegas in distress- most commonly, when they're in pain during heat, menstrual cycles, pregnancy or labor, but also with more menial instances of distress such as anger or sadness.

While Omegas can gain a sense of what an Alpha is feeling through pheromones, Alphas often take on an Omegas feelings as their own, though less severe, and this bond grows stronger when marked or claimed. Marking is most commonly done by giving a mark- a hickey- or licking until an A/O's saliva absorbs into the A/O's gland, though this method is much less potent, exchanging the scent of Alpha and Omega between the two, telling others that they are involved with and A/O. (Please note that biting in attempt to leave a hickey commonly results in accidental claims) This also reduces the amount of pheromones released to other A/O's- A scent-marked Omega will give off weaker heat pheromones and likewise with Alpha's ruts. Claiming, however, is a permanent bond that will almost completely cut off other A/O's ability to smell them.

Claiming is done by biting a partners scent gland until blood is drawn. Fortunately, cases of forced claiming are low, since the bite has to be reciprocated in order for the claim to be officiated, so a bitten Omega will eventually become 'unclaimed', so long as he doesn't bite the Alpha back. This process often takes 1-5 months, but the duration of which is extremely painful for the Omega.

How to Avoid Unconsented Claiming and/or Alphas taking 'Heat Advantage':
- Always carry your wand and have it accessible
- Coat your scent glands with concealers/foul tasting gel 
- Avoid places with a lot of Alphas; especially alone
- Take heat suppressants
- Always keep close attention to when your heat is and take measures to avoid Alphas during that time
- Learn proper defense spells
Advisory: Not all Alphas are dangerous, but all have the potential to be. Even upstanding citizens with righteous morals can become deluded with the scent of an unclaimed Omega in heat or even one just producing strong pheromones.

Harry stared in horror at the last page of the packet. He'd been all over Malfoy during his heat, and nearby Zabini. What if they'd taken advantage of him? According to this, it wasn't uncommon, even for 'Upstanding Citizens'- And two death eaters weren't exactly considered upstanding.

"Rest assured, Mister Potter, we had a very close eye on you at all times," Lauralee assured. "No offense to you, Mister Malfoy, Mister Zabini, but Alphas- especially young as you- have an extremely hard time restraining themselves."

Harry swallowed thickly. "What about... Out there? In the world? How often to Alphas..?"

Lauralee was quiet for a while. "I suggest you take the precautions stated, Potter. Being a male omega is extremely rare- and prized. You'll be heavily sought after by Alphas of all standings- and many are not kind and do not believe Alphas and Omegas are... equal."

"How do you mean?" Luna asked, tilting her head slightly. 

Lauralee glanced at the students faces and sighed, sitting down on her desk and crossing her legs. "There used to be- well, there still are, but there used to be many... rings... that would kidnap Omegas to sell to rich Alphas. There are only a few running today globally, but that doesn't mean you should be unaware. The highest sellers were always male omegas."

Harry's next breath came out stuttering.