Boreal

Boreal is the fearsome beast that guards the Ice Emperor's castle. He used it to freeze the village of the Formlings.

Early Life
At some point, the Ice Emperor was able to tame the beast and it became his loyal pet.

The Last of the Formlings (Flashback)
After the Formlings refused to align with Vex, he persuaded the Ice Emperor to attack the village. Ice Emperor had Boreal freeze the village, leaving most the citizens frozen. The lone survivor Akita had watched her brother Kataru being one of the last victims to the attack and swore revenge on the Ice Emperor and Vex.

Wasted True Potential
Zane saw him in his dream, freezing Great Lake and all five other Ninja.

The Belly of the Beast
Zane saw Boreal in his dream again.

Secret of The Wolf
The Ice Emperor chooses to release Boreal to attack Great Lake. After awakening the dragon with his staff, the beast emerges and flies out to his master.

Appearances

 * 70678 Castle of the Forsaken Emperor

Season 11: Secrets of the Forbidden Spinjitzu

 * 99. "Wasted True Potential" (dream)
 * 102. "The Belly of the Beast" (dream)
 * 121. "Secret of The Wolf"
 * 122. "The Last of the Formlings" (flashback)