I hope this will be something PvE multiple players could engage with. Perhaps something like barbarians but for multiple people at once, so you have to cooperate to take them down. More stuff to do with alliances and friends
Two scenarios come to my mind.
1-Alliances attack with all their members.
2-Each alliance elects one member as a representative, and the others "sponsor" him/her, transforming that member into a "titan" and sending him/her into battle.
Do you want alliances to unite and attack? Yes, it may be epic, but how will they split the reward?