|The Secret of Certavus|
|Series||Bionicle Young Reader|
|Number in series||2|
|Previous book||Journey of Takanuva|
|Next book||Desert of Danger|
|“||A fighter's greatest weapon is his mind. The mind is a more powerful weapon than any sword and a more powerful defence than any shield.||”|
–The Book of Certavus
The Secret of Certavus was written by Greg Farshtey and illustrated by Jeremy Brazeal. It was released on March 1, 2009 in United States and on March 30, 2009 in United Kingdom.
Gresh and Tarix are having a practice match, during the match , Gresh attempts a spinning counter and Thornax Launcher move, only to have it deflected by Tarix. Tarix tells Gresh that he relies too much on the same, and needs to come up with a better variety of moves.
After overhearing the conversation, Berix shows Gresh a piece of a book he found in the desert, with the name "Certavus" on it. Recognizing it as part of the legendary Book of Certavus, Gresh makes a deal with the Agori, agreeing to protect him while he searches for other fragments in exchange for being shown the location of the piece he found.
The two journey into the Wastelands, searching for the book. Along the way, they encounter a vicious pack of Vorox, which Gresh manages to stave off temporarily. Knowing the only way to defeat the Vorox is with a new and improved move, Gresh and Berix hide to the ruins of an old abandoned arena, which is littered with old practice dummies and rusting pieces of metal and debris. As they are looking around, a Vorox tunnels its way inside, attacking Gresh. Berix leaps from the rafters of the arena, scaring the Vorox off with one of the practice dummies. Seeing the Vorox's reaction, Gresh makes a plan, setting up several dummies on the roof of the structure.
In the morning, the Vorox attempt to break through into and invade the arena. Berix and Gresh, however, make the dummies move and shake and create threatening sound effects. Confused and frightened, the Vorox eventually retreats. As they are departing the arena, Berix stumbles upon the Book of Certavus, and offers it to Gresh. Gresh refuses the book, having realized what Certavus would say all along; to fight with brains, and not only brawn.
- In this book, Thornax was mis-spelled and was referred as Thormax.