In Book 6 of the Wheel of Time, "The Lord of Chaos", the Band of the Red Hand came across a massacred caravan of Tinkers. One of the victims had scrawled a message:
Fire had taken most of the wagon lying on its side, but the wagon bed survived, propped on yellow wheels with red spokes. A man in a coat that still showed a little eye-wrenching blue lay hard against it, one sprawled hand black with blood. What he had written in shaky, letters stood out darker than the wood of the wagon bottom.
TELL THE DRAGON REBORN
Tell him what? Mat thought. That somebody had killed a whole caravan of Tinkers?
As far as I know, that question was never answered. Who were these Tinkers, and what was the message supposed to convey?