Leslie explains that in the last few weeks, the climate of Terabithia has been going through unpredictable changes, going from summer to winter without any warning.  She implores Adriana, Tristan, and Insa to help her solve the mystery and they agree.  Diana is named their official liason and guide to Terabithia.  Alone with Adriana, she explains that she is the captain of an elite band of warriors called the Crystal Warriors and that she resents the fact that Queen Leslie called the Phoenix Fighters in for help when she finds her warriors perfectly capable of handling the situation.  Nevertheless, the Queen's advisor insisted on the Phoenix Fighters and Diana agrees to cooperate.

 

The next morning, the four of them set out to investigate.  Tristan and Insa attempt to glean information about Diana, hoping to find a connection between her and Thea.  Diana admits that she was orphaned and is now the last in her bloodline.  Her family fell out of the public interest when an ancestor of hers, Thea's first husband, died without leaving any legitimate heirs.  Tristan realizes that when the Niflheim made the world forget Thea, her children became bastards.  Before they can learn anything more, however, the climate changes drastically and hail falls down upon them.  Diana creates a bubble of ice above them, using her Terabithian crystal - every Terabithian is born endowed with a crystal that has some kind of power - but the strain is too much and she collapses.  Fortunately, the storm passes.

 

Adriana and Diana theorize that whatever is causing the destruction purposely drove them away with the hail.  Insa uses her symbol to determine a sentient being in the center of activity and the group heads back.  Hail assaults them, followed by strong winds which gradually try to separate Tristan from the rest of the group.  Diana just barely manages to hold onto him, freezing his hand to a tree branch and giving Tristan a new experience in pain.  As the weather calms down again, Insa senses a great amount of anger coming to them.

 

An Ebene officer named Darceo emerges from the storm, carrying an unconcious woman with him.  Diana immediately recognizes her as Vesta, a Terabithian who possesses the crystal which controls climate.  Darceo demands Tristan come with him, or else he will kill Vesta.  They realize that Darceo has been posing as Queen Leslie's advisor and that he arranged everything to get the Phoenix Fighters to come to Terabithia for the sole purpose of kidnapping Tristan to use as a bargaining chip against the Niflheim.

 

Tristan willingly gives himself up.  As Darceo tries to tie him up, however, he stabs the Ebene soldier in the throat with Insa's flint knife.  Diana casts an ice bubble over Vesta while Tristan managers to kill Darceo.  Vesta is rescued and the team returns to the palace where they are greeted as heroes.  In return for their services, Leslie gives the Phoenix Fighters some magical crystals, a few goats, and most importantly, permission to call on the Crystal Warriors in a time of need.  Tristan tells Diana he believes they are related.  Diana is surprisingly receptive and calls Tristan family.