The Antler Men are a group of rich traders and merchants of King's Landing.
A Clash of Kings
The Antler Men plot betrayal against King Joffrey I Baratheon and intended to abet the fall of the city to Stannis Baratheon. They name themselves after the crowned stag of House Baratheon, apparently not knowing that Stannis has changed his sigil and replaced the crown with a fiery heart surrounding the stag. They arm several hundred men and plan, once fighting between Joffrey's loyalists and Stannis's forces has begun, to seize the Old Gate and let the enemy into the city. Master armorer Salloreon is a member of the group.