The Trade floor guard is an Elite Black Guard soldier assigned to protect the Trade Octagon from would-be thieves. They are identical in appearance to Black Guard Berserkers, but are stronger.
If a player fails to pickpocket a dwarf trader, one of the trade floor guards may attack. The player has two options to prevent the guards from interfering with trading:
Talking to the director that they aligned themselves with in The Giant Dwarf; after completing a task given by the director, the guards will ignore the player for 10 minutes.
Luring the guards away from the trade floor and into one of the company offices, ideally The Blue Opal's office to the west and The Silver Cog's to the east, before closing the door on them. They will lose aggression but not be able to leave the office (as their wander range does not cover the entire floor), provided that the door is not opened or they are killed, however if left in a position, where they cannot move to another tile, they will eventually respawn.