AFK is a game feature, unlocked at level 20, that allows players to automatically use their skills in battle. Priority appears to go to the highest rage-consuming skill available, regardless of its usefulness and QTE events are triggered.
It can only be used against mobs where no other players are involved such as Campaigns, Forgotten Catacombs, World Boss and Wandering Managogs.
All players defending in the arena and plunders are also under 'AFK' control and follow the same rules.