Bella learned some arguably important lessons during her fight with the headmaster.

The first thing she learned was that if she suspended the movement of the atoms within something, she would change it's structure in a very specific way. She used her replacement power on the vines around her so that they wouldn't move, something she barely had to focus on for it to happen. Her control truly did translate to the new power.

She'd originally meant only to stop the growth, but found herself stopping the movement of every atom within the plant. Sure, it had the same result since a dead plant can't grow, but it wasn't her true intention.

It didn't die immediately, thankfully. It stayed alive for most of the battle, in fact. Bella was able to grasp onto the parts of the vines that didn't hold thorns and use them to climb over the wall the headmaster had formed around her.

Once Bella jumped down, she counted the seconds until the headmaster caught her again. Based on the initial catch, she estimated 15 seconds during which the headmaster would continue to torture her with elevating heat, but likely making sure her internal temperature didn't get so high that she might die.

Though, there was always the chance that the headmaster wouldn't care if Bella had brain damage or some other type of serious problem as long as death wasn't the end result, so Bella wasn't going to go ahead and let the torture continue for long.

15...

Bella focused her energy on using her power against the headmaster. Movement wasn't a necessity for her, clearly, but she was using three different powers at once: Mitch's ability to grow and control vines carrying poisonous thorns, someone's fire-related ability, and Bella's own telekinesis. It had taken her a few moments to realize, but her telekinesis alone wouldn't have been able to do damage of this sort. The telekinesis, Bella realized, wasn't even directly being used against her. It was being used to protect the headmaster.

It seemed the headmaster thought Bella might attempt something Bella didn't even know was possible, something Bella's imagination couldn't even fathom.

14...

The telekinetic field had been taken down by Bella's use of her power. They'd counteracted each other and so neither party could do much in the way of attacking each other that way. Unfortunately, the headmaster had the upper hand with the use of two other people's powers.

13...

Bella began to feel sick, as if she might throw up right where she stood. The room was beginning to spin and there was just about nothing she could do about it. Only one power remained in the headmaster's arsenal and she was using it to it's fullest power.

12...

And then she backed off a bit.

Just as Bella thought, the headmaster liked to play with her prey. It would be her downfall, her fatal flaw, so to speak. Bella didn't like to play, she liked to win. She liked to protect those important to her, she liked to get revenge, and she liked to win. She really like to win.

11...

Just as Bella felt another onslaught of the headmaster's "fun" with heat, Bella used her power on the ground beneath the headmaster. Stilling matter wasn't the only thing she could do with this power. That was something she'd learned while fighting Kaiya. It was the opposite of telekinesis in many ways, but it wasn't the exact opposite. There were similarities.

Telekinesis was the ability to control and manipulate matter, the opposite of which would just be the inability to do so, except essencists couldn't just take your power. They had to replace it with something, something that was as close to the opposite of your power as possible. Most powers were easy: the opposite of fire is water, the opposite of darkness is light. Others were a little more difficult, but feasible: the opposite of telepathy was reality warping, the opposite of invisibility was the ability to make all things visible. These things cancel each other out. If you fight fire with water, they'll both fizzle out. If you fight darkness with light, the result is a tie. If you fight telepathy with reality warping, both parties are confused and unable to continue. If you fight invisibility with complete visibility, no one has the upper hand.

But none of these are technically the opposite of the ability itself. The opposite of the ability itself would be an inability.

That was the conversation Bella had with Kaiya over breakfast and that was how she figured out how to beat the headmaster now.

10...

Opposite powers have similarities. For Bella, the similarity was that she could still manipulate matter to an extent. She could compress it so much so that it caused a hole to form beneath the headmaster's feet, one that she couldn't get away from quickly enough because her focus was elsewhere while Bella's was only on one thing.

9...

The headmaster fell straight through the hole and Bella felt herself cool down almost immediately. She smiled, knowing that just as it had been with Hades and Professor Allistair, she'd won. This was the signal that she'd won.

8...

There was silence throughout the dome as everyone looked on to see if the headmaster would come back up.

7...

Some security guards and a healer took a few steps toward the hole to help out if the need arose, but stayed far enough away just in case the headmaster was furious and wanted heads to roll because of her loss.

6...

The silence began to die down as spectators began whispering to each other, likely not having believed Bella had a chance because this was the headmaster. The headmaster.

Wow, this was the headmaster. Bella couldn't help but smile at the fact that she'd just beaten the headmaster. Maybe she could finally relax.

5...

The sound system buzzed to life as the announcer began to declare Bella the winner of the Mallent Talent Competition.

Bella looked around, realizing that the vines she'd been trapped in before was now just a pile of ash, or at least that's what it looked like.

4...

Something felt off, but Bella ignored it, basking in the moment. She was being announced winner. The headmaster could take her threat and shove it because there was now nothing she could do to make Bella do anything she didn't want to do.

3...

The crowd erupted in cheers and Bella had to wonder if this was what it felt like all the time for heroes. Do people cheer for them? No one had ever cheered for her and it felt like a weird mixture of feelings. One part uncomfortable, one part absolutely amazing, and one part chilling and not in a good way.

2...

The security guards and the healer took several more cautious steps toward the open hole and Bella suddenly realized what felt off.

Her powers.

Her powers hadn't returned.

There was the first battle with Kaiya when the same thing happened, her powers didn't return, but that was because she beat Kaiya on a technicality. Kaiya could no longer fight, but she wasn't unconscious. It was when Bella had knocked Kaiya unconscious that Bella's powers returned immediately.

The headmaster, though, would never allow a loss. Being knocked unconscious would be the only way she'd lose. Bella knew that. Everyone knew that.

1...

Bella felt the heat return to her body, though she couldn't see the headmaster anywhere. Moments later, the vines began to grow around her again and Bella had no fight left in her. She'd used everything.

Besides, without her powers, her real powers, she couldn't fight someone she couldn't see and the headmaster didn't seem like she'd be showing her face anytime soon.

The crowd quieted and the various staff members rushed back to the sidelines where they felt more comfortable. They were out of the way and in no danger over there. No need to be hit by a stray poisoned thorn, right?

The cat wasn't quite done playing with the mouse, though, Bella realized. That was the worst part. Bella knew she couldn't win and knew the headmaster was just toying with her instead of ending the battle quickly as anyone with a heart would do.

Bella knew she didn't have the best luck, but to be toyed with like this was another level...

Luck.

Of course! Bella suddenly remembered the gem Hades had given her. She wasn't sure how it worked or how she'd know if it worked, but she knew it was really her only hope of winning. A piece of his sister would disappear with the use of it, but he had encouraged it.

No sooner had Bella thought about using it than she felt the ground beneath her crumble, followed immediately by the feeling of her own weightlessness as she fell through it. She expected to hit the ground, but before she could her hand became entangled in the vines that seemed to be holding onto the ground above, the part that was still intact anyway.

Those vines were much stronger than Bella ever thought they'd be. They held her up seemingly without a problem, not tearing in the slightest at the sudden added weight. Despite that, despite the fact that she managed to find the headmaster- who was now standing almost directly below her- and despite the fact that she'd managed not to break anything during the fall, she was pretty sure she'd managed to dislocate something. Her right arm would certainly not be of any use to her until she got to a healer.

Through the pain, Bella learned something very important about herself: the closer she feels she is to losing everything, the more villainous she becomes.

Seeing the headmaster and feeling the complete weakness and brokenness of her body brought to her a feeling she'd never felt, not even before beating Hades. She felt drained- physically, mentally, and even emotionally- yet she'd never felt more powerful. She believed this was what villains felt every day, why they could keep fighting even when they almost always lost, and in that moment, she was drunk on it.

The feeling was like no other and she was going to use this new drive to her advantage.

Bella had an idea, one that would work to her advantage, but first she'd have to bottle her anger for long enough to focus on getting down.

Bella's eyes met the headmaster's and she realized that they were both absolutely done with the fight. One of them would win this time. No more games, no more chances.

The vine began to wrap around Bella's arm and continued wrapping around her until her entire body was dressed in them. Just as they began tightening and Bella could feel the sharp edge of the thorns on several points on her body, the vine snapped and Bella fell the rest of the way to the ground.

The last thing Bella learned in her battle with the headmaster was that villains considered their rules as things to be twisted, bent, and manipulated, but never to be broken.

Bella had not broken the rules.

She'd used no formalized fighting technique, only her powers and a little bit of luck. The headmaster was not dead; Bella could feel the movement of her chest beneath her, signalling breathing even if nothing else.

Bella felt her powers return to her and knew that this time, the battle had been won. She'd managed to defeat the headmaster, even if it was mostly luck in the end and had little to do with her own abilities.

The sigh of relief that followed her win was almost involuntary. The feeling of accomplishment and pure joy was more than welcome, but the foggy and distant feeling that came soon afterwards was something Bella could have done without. Bella sat up and began to feel the many different areas where she'd been pricked by Mitch's annoying poisonous thorns.

Of course, Bella thought as she stood to her feet. She saw people rushing toward her and smiled slightly before her strength gave out and she fell to the ground. Her vision faded and the sounds around her seemed to go off into the distance, but she couldn't help but feel happy about this.

Bella really hoped there was an afterlife because she really needed to meet Hades' sister, even if just for a moment, to thank her several times over for this small gift.

*******************************************

I'm no scientist, but this is what happened in my head so this is what happened in the book. Of course it's not scientifically accurate, but neither is having superpowers, so let's just play pretend here.