SOMEONE TELL ME WHAT YOU HAVE TO DO IN THIS CATEGORY ? <-- Translation
The aim of assassins is to gather currency through chests around the map and use the currency to purchase various items from different shops I.E. food, armour, potions, weapons
You also have to kill other players and pvp is enabled everywhere except the shop, so steer clear of other players if you are carrying a large sum of money on you. There isn't really any other goal besides to kill people and gather money to purchase better gear.