First, you need to get the Golden Arhat Badge itself. To do this, defeat the Second Prince and the King of the Flowing Sands, activate the Valley of Despair altar on the left and enter the cave. Go down to the bottom of the cave, to the pit. If you killed only the Second Prince, the King will summon the First Prince. If you killed the King and the Second Prince, then go to the pit and throw the King's flesh to summon the First Prince of the Flowing Sands. After defeating him, you will receive the Golden Arhat Badge.
Now you need to complete the Drunken Boar quest, during which the Golden Arhat Badge is used. We talk about this quest in more detail in a separate guide. The Golden Arhat Badge is needed to force the boar in the yellow monk's robe to attack you.
The action game also received a content update.