Hero of Ideals

Zekrom was commanded by the Hero of Ideals one thousand years prior to the events of the films. At the end of their war with the Hero of Truth and his Reshiram, it returned to the form of a Dragon Stone and was sealed away in the caves inside the Sword of the Vale. During the actual events of the films, Zekrom helps Reshiram save the world from the corrupted Dragon Force by funneling it into the Sword of the Vale. It also aids by trying to destroy the Protecting Pillars and then by helping guide the Sword of the Vale back down to the ground.