New tower mini dungeons have been erected around the world! These places seem to attract particular types of beasts, but that's no matter because you'll want the stuff they have. On certain days, or times of the day, 5 new boss type enemies may settle at one of these towers (or maybe more than 1 at a time). As long as they are there, you can run through and fight them, whether by yourself or with your trusty teammates.
You'll want to take advantage of these bosses while they are around, because you'll never know when and if they'll be back. In addition, they hold the pieces of the Level 100 equipment sets. Each piece grants stat boosts and buffs and can be used by any class! You won't be able to get these pieces of armor anywhere else!