The Arena is perhaps the greatest meeting place in the world of NinjaManager, with thousands of battles taking place every day for gold and experience.
There are different statuses for teams which determine if they appear in the arena list or not.
Teams that have been active in the last 20 minutes, which means they have spent either arena energy or world energy.
Teams that have not been active in the last 20 minutes, but have been saving up AFK time and is now using that to stay active for a bit longer in the online list. AFK time is earned by spending arena energy. 30 seconds of AFK time is earned for every 1 arena energy spent. For example, spending 120 arena energy would make your team stay in the online list for 1 hour after you have logged off or gone inactive.
Teams that are currently offline are shown in the offline list, which is shown in case there are not enough teams in your filtered online list.
Teams that have not been seen for over a month will be tagged as retired, and won't show up in the offline list. They will however still be available in the game and up for receiving challenges! Should their owner return, their retired status will be removed.