My friend and I had a random idea of a tower public event in which the tower is invaded or breached and you would have to repel the attackers. Perhaps it could start in the city below and have to fall back to checkpoints as harder and harder waves appear. Just a thought to add a little extra excitement. However it's not completely thought out, if you can think on how to make this better or tell me how it might not work I would love to hear it!