Battle Royal is a 3 day event where guilds with level 25 castles can battle it out in a type of Capture The Hill style wonder fight. Where the guild member to hold the wonder the longest wins. This event takes place in the Royal Battleground. You can find the Royal Wonder at K:71 X:256 Y:512
It costs 100,000 gems to participate and only castle level 25 turfs can enter by purchasing the Royal Pass.