Hunter Games is mixed PvE and PvP gamemode that takes place at Channel 4 in Eldeon Castle. You must be at least level 150 to register for the Hunter Games. You can find out when Hunter Games will take place by using the Server Calendar (Start -> Features -> Server Calendar) or registering for Discord notifications.
When the Hunter Games take place, all players will be teleported into the Hunter Games arena. There, monsters will spawn. When defeated, these monsters will grant the player Hunter's Gems, which can be used to unlock the 5th Monster Card Slot in weapons.
However, you can also kill players to steal their gems and kill their monsters.
Be careful who you pick a fight with! You only get as many gems as you leave with, and if you decide to PvP someone, don't expect them to not retaliate!
At the end of the Hunter Games, there will be safe zones that you can exit the arena from. You only get to keep as many Hunter's Gems as you leave the arena with, so don't get too greedy!