The white robots are reused props from a production of Reason by Isaac Asimov. In-Universe, that suggests that they're repurposed fictional characters just like Gulliver and the Karkus. Moreover, in both stories their allegiance is only to The Master.
The main danger in this story is of real people being turned into fiction. The sword fight really emphasises this threat when you consider that Cyrano de Bergerac was a real writer and duelist from seventeenth century France, D'Artagnan was a real captain in the King's Musketeers who could well have known Cyrano, and Blackbeard was a genuine Caribbean pirate whose real name was Edward Teach. Only Lancelot is pure fiction, and even he could well have had historical predecessors in the lieutenants of the real person who became King Arthur. In other words, four men who had already been turned into fiction.
And if the Master is indeed Samuel Bracebridge Hemyng, that means in a roundabout way that has already happened to him, too.
