This NPC doesn't just sell maps; they sell . They are likely a rogue or a wizard’s apprentice who specialized in Arcane Eye or invisibility just to get a peek at the loot. Character Profiles
That sounds like the perfect setup for a with a "high-risk, high-reward" quirk! Here are a few ways to flesh out that character: Sees what the dragon hoards, draws the maps NPC...
An artist who believes a dragon's hoard is the only subject worthy of his talent. He isn't there for the gold; he's there for the composition . Plot Twist Ideas This NPC doesn't just sell maps; they sell
The NPC sells the party a map of the hoard, but the dragon moved half the treasure to a different chamber yesterday. Here are a few ways to flesh out
The NPC is actually a transformed dragon or a mimic who lures greedy adventurers into the lair to provide the "hoard" with fresh gear (and the dragon with a snack).