Sentinel Knight was pleased to see that Mack stayed and still wanted to help.  He told the young man about the Sword Excelsior and how he believed that Thrax planned to capture it and use it to destroy Sentinel Knight.

Against the Knight's wishes, Mack went in search of the Sword.  After reading up on the weapon, thanks to a book at Rose's university, Mack found the sword in the Warrior Goddess statue in a forest.  However, Thrax had followed him there and planned to take the sword for himself.  The other Overdrive Rangers showed up to help Mack.

When Thrax tried to take the sword, it remained in the hands of the statue.  The Warrior Goddess would only release the weapon to one she believed to be true.  This caused Thrax to vow revenge on Earth.  

The team tried with all their individual might, but they could not release the sword.  They were ready to give up, but not Mack, he refused to leave without Excelsior.  So he and Overdrive Rangers tried together as one to free the sword.  The Warrior Goddess came to life then.  She explained that through their friendship and conviction in their hearts, he knew the Sword was theirs.  Excelsior was then given to the Overdrive Rangers.

Later the team gave Excelsior to the Sentinel Knight.  The Knight and the Sword then bonded together as one.  This restored the Sentinel Knight's power, and granted him a newer form.

With Excelsior & the Sentinel Knight being as one, when in sword mode the Rangers can use the weapon in battle.  Then by turning the knob, they can release the Sentinel Knight for him to fight along with them.

Excelsior is also a key element in activating the Red Sentinel Ranger.  The Red Ranger presses the activation button on the Battlizer Morpher, and then activates the Sentinel Sword to Sentinel Knight mode, to then morph he and the knight into the Red Sentinel Ranger.