Jack was worried, and justifiably so, he felt.

He was still sitting in Tooth's lab, out of the way of the student classroom, studying the slime based mixture he had found in the forest.

Of course it wasn't the slime that was worrying, well it was worrying, but it wasn't as worrying as the gritty oil like substance he had found mixed with it.

According to all his tests, it was natural rot, condensed and purified - if you can 'purify' rot - until you got the oily fluid. Of course it would take a serious amount of magical power to create such stuff, especially if the Forest Spirit was doing her job.

The slime suggested she was, but also that she was the one trapped in the rot.

Jack, despite the amount of time he spent in the forest, had only met the Spirit responsible for it's upkeep twice. And quite honestly he was surprised that the rot was powerful enough to subdue her, or even contain her because she was obviously still fighting.

Jack sighed and rubbed a hand through his messy hair. He had been looking at this stuff for the entire weekend and all he was doing was praying that the obvious answer was not the answer at all.

Because if the rot was attacking, it would aim for the school. It took a lot of magical energy to make pure rot and the school was alive with it, literally, those kids were lucky they got out and hadn't had their magic sucked dry.

What was worse still, until they found it or until it found them, there was nothing the Guardians could do to stop it.

"Hey, Jack, any luck?"

Tooth fluttered in through the door to the classroom, coming back from dinner, Jack thought with a glance to the clock on the wall.

"Only if your idea of luck, is bad." Jack was tired, he couldn't even be bothered thinking of something witty.

The Guardians were immortal, they didn't need sleep, but sometimes they could be mentally exhausted.

"So you know what it is?" Jack would have joined Tooth in her excitement, but she didn't know what it was yet.

"Purified rot."

Tooths wings stopped beating, for a fraction of a second, before she caught herself from falling.

"Bu-But that's…"

"Bad. Very, very bad."

"It going to try attacking the school, isn't it?"

"...probably, and there's not much we can do to stop it before it comes." Jack took a deep breath before continuing, "Tooth, it has the Spirit of the Forest trapped."

"Oh dear…" Tooth, like all the Guardians, knew the importance of the Nature Spirits. Jack himself was one, one of the four season's even. Even Bunny was connected to nature even if he wasn't necessarily part of it. "We better tell the others."

"Yeah… thanks Tooth."

Sighing Jack left Tooth's private lab, heading towards North's office. It wouldn't do to let the other teachers know, until they really, really needed too.

Knocking twice before pushing open the large door, Jack couldn't stop the small smile on his face at the sight of the toymaker. Bent over a large block of Jack's permanent ice, North was busy chiseling out a small and perfect train set.

"Hey North."

With a slight jump the large man turned, not having heard the knock on his door.

"Jack!" The ready welcoming grin faded slightly as North took in Jack's tired and serious expression.

"You know what it is?"

"It's not good, North, Purified rot…"

Before Jack could continue with his explanation, North up one of his massive hands, interrupting him.

"I'll call the others, they need to hear this too."

Jack only nodded in reply, already thinking of ways to train to students to avoid the Rot. Fast track the flying lessons, he thought, get them out of there.

Within minutes, North's message reached the Guardians, the shining light that only they could see travelling down the corridors of the castle.

It wasn't long afterwards that Sandy floated in, followed closely by a harried looking Bunny. Tooth fluttered in a minute later.

Bunny, who had opened his mouth to complain, noticed the look on Jack's face. It was a well recognized fact within the Guardians, and the Spirit World in general, that if Jack looked that worried about something, it couldn't be good.

"Oh, this isn't going to be good, is it?"

Again Jack only shook his head, he hadn't been this tired for ages. He might have to get Sandy to knock him out for a few hours, give his pounding and racing mind a rest.

"Purified rot."

In two words, the look of dread on Bunny's face changed to one of horror, the other Guardians may not have known what it was. The other's knew that it was bad but Bunnymund, with his home in the Warren and connection to plants and life, had more knowledge than most. He knew precisely what it meant.

North, it seemed, did not fully register the looks that Bunny and Jack were exchanging. Either that or he was trying desperately to be optimistic.

"Well, now we know what it is, we go out and kill it. Yes?"

It was Bunny's turn to shake his head. Even the Guardian of Hope, would not dare to hope for it to be that easy.

"No, North, we can't just go out and kill it." Jack said quietly.

Shaking himself mentally, he couldn't just let it stop him now, Jack dragged his mind back from the yawning pit of despair and began working on a solution.

"Purified Rot," Jack began in explanation, "is a highly magical, and destructive substance."

Well that was a good start, Jack thought, Bunny was nodding in agreement and he had the full attention of the others.

"It feeds of magical energy, and multiplies itself that way. It is not a wholly sentient form, though it does have a purpose once given form. So not only do we have to worry about the Rot itself, but whoever created it."

Damn, that was something else he had to worry about, at least that list was smaller.

"Not only that, but it has trapped the Spirit of the Forest, at first I thought it was the thing controlling it. I seems I was wrong."

Sandy came forward, symbols flashing above his head, Jack had to squat in front of him in order to follow more closely what the little man was saying.

Alright. How do we fight it?

Jack let himself grin slightly. Thanks Sandy.

"I'll be able to freeze it, weaken it that way. But other than that it takes a special form of creation magic to stop it."

"Creation magic? Is that not a little opposite to what we're looking for?" North asked.

"No, the rot is...destructiveness solidified. To hurt it you use it's own matter to create. Bunny's magic should be useful here."

Bunny nodded. Rot might be death to all living things, but once frozen and 'deactivated' then it made a great fertilizer.

"The hard part'll be gettin' the Forest Spirit out o' there wi'out hurtin' her." Bunny concluded, he could show the other Guardians a little creation magic without too much hassle.

Jack smiled genuinely now. Maybe it wasn't as hard as he thought it would be.

"Not really. My magic will only send her into hibernation, it shouldn't kill her or cause any lasting harm. Nothing that she can't fix anyway."

"Excellent!" North was getting enthusiastic again, and for a minute Jack let himself be caught up in it.

That was until he remembered, there was no way to find it, they had to wait until it came to them.

"Uh...North." North who had been getting ready to grab his swords and march into the Forbidden forest stopped, looking at Jack expectantly.

"We have to wait until it comes to us. There is no way to actually find the stuff, not in the forest. It was only luck that those three kids found it, let alone survived it."

As quickly as the excitement had set in, it faded, until Sandy came forward again. A determined look on his face.

Then we wait. And prepare the students the best we can.