Players usually go to Blood Castle to get experience. There are many monsters, so you can level up fast. You can also win the event, get a reward, and add a win to your event ranking. To do this, you need to:

• Kill the number of monsters indicated in the lower right corner. The number of monsters depends on the number of participants.
• Destroy the Castle Gate.
• Kill the number of Magic Skeletons indicated in the lower right corner. (The number of "Magic Skeleton" depends on the number of participants.)
• Destroy the Crystal Statue.
• Pick up the Archangel Weapon You need to give it to the NPC in the starting area of the event.  You can give it when there are less than 60 seconds left before the event ends. 

To enter you need Blood Castle Ticket, you can buy it or get as Reward. Also you can use for entering Invisibility Cloak, which can be crafted in the Chaos machine: