After Flurious and Moltor tried to steal the Corona Aurora and were subsequently cursed, the Sentinel Knight hid the crown and its five jewels throughout the planet Earth.
His spirit returned after a few hundred years to urge that Andrew and his team of Rangers protect the crown from impending forces. He once battled and imprisoned Thrax , the son of Rita Repulsa and Lord Zedd.
When Thrax disabled the Overdrive Rangers' powers, Sentinel Knight summoned five veteran Rangers and repowered them so they could temporarily take the current Rangers' place.
After Mack retrieved the sword Excelsior, he gave it to Sentinel Knight so that no one could use it to harm him. Excelsior restored Sentinel Knight, and fused with him, granting Sentinel Knight a new physical form.
After being restored to a new physical form, he swiftly destroyed Thrax. He has since been capable of transforming into the powerful Sentinel Sword weapon. Thanks to modifications by Rose, Sentinel Knight was able to merge with Mack to become the Red Sentinel Ranger.
When the Corona Aurora was successfully retrieved, the Sentinel Knight took his original form, but is still able to combine with Excelsior. Thanks to Sentinel Knight, Mack became human when Sentinel Knight placed the crown on his head.
- While he does have a Sentai counterpart, his original "spirit" form was not in Boukenger.
- The Sentinel Knight plays a similar role to Ninjor from Mighty Morphin Power Rangers Season 3.
- Nic Sampson, who voiced the Sentinel Knight, also played Charlie Thorn in Power Rangers Mystic Force.
- Great Sword Man Zubaan - Super Sentai counterpart in Boukenger.