Dungeon merchants are vendors that require tokens acquired from a dungeon in exchange for goods. Like merchants, these NPCs have a "[Merchant]" suffix after their name and a normal merchant icon. All Dungeons merchants were replaced by the Dungeon Armor and Weapons merchant in Fort Marriner in the rebuilt Lion's Arch.
List of dungeon merchants
Lion's Arch (the Dungeon Armor and Weapons merchant in the rebuilt Lion's Arch)