The idea of a Wandering Sentinel was conceived as a way to contrast with villains motivated by revenge, fear and personal motives. This character would feel like they are doing the right thing, despite opposition from the people of Mobius.
The Sentinel was originally an echidna who grew tired of his warlike people during the Great War. The warrior betrayed his own kind, hoping that the Drakon Empire would bring an end to the suffering. However, he soon found out the Drakons' true personalities but was unable to escape. The Drakons made sure he couldn't by trapping his soul in a robot sentinel. This stopped the echidna from returning to his people, realizing that they would only see him as a treacherous robot. Instead, the sentinel stole a ship full of other sentinels and left, knowing that as long as other sentinels existed, his soul could flit in and out of them.
Over the years, the Wandering Sentinel frequently protected Knuckles the Echidna. He hopes that he can convince Knuckles of his true nature and that the spell that put him here will be made redundant. Until then, he continues to face persecution from the likes of Sonic the Hedgehog.
- The idea of the Wandering Sentinel likely derives from the story of the Wandering Jew.