mechant mark are usefull pieces,that you can exchange vs alot items in the exchange tent shop on city fair location.....potions,caskets,belts,pets,talents for example you receive the mechant marks for daily log in....day1 5pcs,day2 10pcs and day3 15pcs also can receive 20pcs from casket,that we receive from daily activity in especially caskets,boxes trunks etc too and on mirror magic event