The is a free, standalone mobile game that syncs with your Ubisoft account (Uplay/Ubisoft Connect). Unlike modern bloated companion apps, this one served a single, glorious purpose: letting you play the Arena offline on your phone to earn in-game currency and XP for the main console/PC game.
Whether you use the app or not, remember Pagan Min’s advice: “Kill, or be killed. That is the only truth in Kyrat.” Now go earn that Bushman. far cry 4 arena master app