User blog comment:InGen Nate Kenny/Telltale reveals a major Riverlands house's existence in TV continuity?/@comment-5014364-20150919152625/@comment-26569935-20150919175848

He's confirmed to be from Blackwood lands, not implied. Smallfolk have made journeys that far, and even further. For example, Ros went from Winterfell to White Harbor. So there's that.

I don't understand that second part though, because by what logic? This was a lord's son's knife, and more often then not nobility but their sigils and heraldry on their weapons and armor (see the various shields in the series).

Designs have been changed, but the gold swirly line is what I interpreted as the silk.

The point is that Finn killed a lord's son, presumably from the Riverlands, and that knife likely had the sigil of said house there. I understand your comments, they are quite valid, but I think with the stuff we have and Arthur von Nagel's comments can prove its existences.