The Minosian peddler is an automated holographic salesman who greets visitors to the dead world Minos and demonstrates the Echo Papa 607 weapon system that wiped out its makers.
The peddler appears in The Arsenal of Freedom. When the Enterprise-D arrives at Minos in search of the missing USS Drake, a recorded image of a cheerful salesman hails the ship and urges it to buy from the arms merchants who once supplied both sides of the Erselrope Wars.
The planet has no living inhabitants. The peddler is merely the front end of a sales demonstration for the Echo Papa 607, a self-improving weapon that sends ever more capable drones against its targets, and which destroyed the Minosians themselves.
Picard, trapped in an underground control room with Beverly Crusher, summons the hologram and ends the attack in the only way the programme allows: by telling the salesman that he will buy the system.