Mu Online/Chaos Castle
Chaos Castle is an event where all the competing players are placed against each other along with some monsters in a free-for-all deathmatch. To enter, an armor of the guard must be purchased from a shop. When a notice appears that Chaos Castle is about to start, you can click on the armor and it will send you to Chaos Castle. You must pay a fee to enter, depending on your level.
Before Chaos Castle starts, a random competitor would be awarded all the fee the players paid to enter this event.
All of the participating players will appear to be wearing the same armor, and each class will appear to be wielding identical weapons, but their inventories won't actually be altered in any way. Notice that players may wear their wings but have to get in without driving a pet. Once Chaos Castle has started, it will fill up with look-alike monsters until it contains 100 characters. Some of this monsters are traps which explodes when killed, killing players near it. Monsters also drops jewels upon death. While the players are fighting, the castle will start to perish and break up from the sides, doing so until there are only around six player squares left. In order to complete the event, a player must survive through the event and eliminate all of the other participants. The winner will receive a Jewel of Life or Jewel of Creation or a very slight chance of getting an Ancient item.