Robot Knight

The Robot Knight first appeared in Dragon's Lair, and later in Dragon's Lair 3D Return to the Lair.

Dragons Lair
The Robot Knight attacked Dirk by activating electric panels under him, but was later defeated by him.

Dragons Lair 3D: Return to the Lair
The Robot Knight appeared again in Dragons Lair 3D: Return to the Lair, where he used the same tactic, but this time if you defeated him, you would get The Power Ring

Trivia

 * The Robot Knight got his name from Dragons Lair 3D: Return to the Lair, when he was called this.