World Events are as yet an unimplemented feature. Basically, I think the game has not yet progressed to the point where they are feasible within the scope of the developers’ vision.
This could be because they involve alliance vs. alliance challenges. Or it might involve a Tournament of Champions. It could even be a race to complete a set of goal-oriented tasks. Right now, we don’t know. Whatever shape they take, I for one am looking forward to their implementation.