Swamp of Secrets is Out!

Check you local bookstores for details. Unfortunately, I don't have the book yet, so I cannot reveal any spoilers. But, according to Biosector01 (found in the Bionicle Link List) the spoilers will reveal:

Takanuva will appear in the introduction.
Why Tahu was chosen to be the leader of the Toa Mata.
The name of the First Toa.
Which Makuta knocked one of Krekka's eyes out.
Which Makuta conquered the Visorak to use as a Brotherhood of Makuta army.
The storyline significance of the "Bohrok and Balta" sculpture in the Order of Mata Nui's headquarters.
The Order of Mata Nui Leader will make an appearance.
Krakua will also appear, this time in the present.
Brutaka will appear in a most unexpected way.

Also, Greg previewed this a long time ago:

(an excerpt)

The crimson-armored being opened his eyes and looked around. He did not recognize where he was, nor did he have any idea who the five figures nearby might be. Each of them was lying on a slab, just like him, and each wore colored armor and a mask. But where he was red, they were other hues: white, blue, green, black, and brown.

Of course, it came as no great surprise that he didn’t know who these others were. After all, he wasn’t sure who he was, either. He started to rise, then found he could not. Thick metal straps encircled him, keeping him pinned to the slab. Unsure of his identity as he was, he still knew that he didn't like being bound. He tried to exert his strength against the bonds, but without success. His frustration and anger grew. And then suddenly the metal of the straps was growing soft, turning to molten liquid, running off him and onto the floor.

Did I do that? he wondered, as he sat up.

On the next slab, the white armored figure had frozen his straps and then shattered them with the merest gesture. The others had all found unique ways to escape their bonds as well.

“Well, we’re all free,” said the red armored being. “Now what? Anyone know where we are … or who we are?” The answer came then, but not from any of them. Rather, it was a voice that seemed to come from every part of the room that spoke in reply. “You are Toa.”

The figure in the brown armor jumped down from his slab and onto his feet. “Toa! Hey, that’s great. I always wanted to be a Toa.” He looked up and addressed his next words to the ceiling. “Just one question: what’s a Toa?”

“A Toa is a hero,” the voice answered. “Every Toa commands an elemental power, which can be focused through your weapons. Each of you also wears a Great Mask, with a power all its own. You will learn about these powers in time, as well as how to control them.”

The white armored figure frowned. “To whom are we meant to be heroes, and why? You say we have great abilities, but what are we meant to do with them? Too many questions, for my taste …”

The unseen speaker laughed softly. “You underestimate yourself, Kopaka – yes, that is your name. Questions will always whet your appetite for answers. But now it is time for you to meet.”

A lightstone illuminated on the ceiling above Kopaka, as the voice said, “Kopaka, Toa of Ice.” One by one, the lightstones lit above the others as the speaker recited their names.

“Gali, Toa of Water.”

“Pohatu, Toa of Stone.”

“Onua, Toa of Earth.”

“Lewa, Toa of Air.”

The last to be named was the crimson armored figure. “And Tahu, Toa of Fire. He will be your leader.”

That seemed to startle Kopaka, who said sharply, “It seems to me we should be allowed to choose our own leader.”

“I have to agree,” said Gali quietly. “I mean, none of us know anything about this Tahu. What if he’s too impulsive to be a good leader? What if he lacks the ability to work with his team members, or can’t motivate, or --”

Lewa chuckled. “Or what if he’s just a jerk?”

A bolt of flame shot from an irritated Tahu past the Toa of Air, close enough to heat his mask to an uncomfortable temperature. Lewa reached up and yanked the mask off. Immediately, he felt so weak he almost fell over. Pohatu and Onua rushed to support him.

“You must not remove your masks, unless you are replacing one with another,” the voice said. “Without them, your strength is halved.” Lewa gingerly returned the hot mask to his face. “Thanks … ow! … for telling us.” He turned to glare at Tahu. “And as for you, fireflyer, better be careful a big wind doesn’t blow you out one of these days.”

“Big wind,” Tahu said, nodding. “Yes, that’s you, all right.”

Kopaka decided to ignore the argument. “So we are a team,” he said to their unseen host. “Again, I ask – for what purpose? What are we meant to do?”

A panel slid open in the far wall. Beyond, there was only darkness.

“The gateway to another mystery, perhaps,” said Onua. “I wonder if a Toa’s life is filled with them?”

“Then this will be just the first of many we walk through,” Tahu replied. “Let’s go."

So, go to your local bookstore now! Bionicle Legends 10 awaits you.
When I get it, I might reveal some of it.

I hear it's quite epic and full of intense battles.