Here's another valentine's or easter or whatever event idea...
Add a wilderness that has a 24 hour lifespan,
and spawns with about 2.5 or 5 million units scale inside it.
You heard me.
2.5 million or 5 million units inside it.
About equivalent to a level 6 wonder maybe.
Killing this wilderness should grant extremely high quality loot with valence equal to the fact that the majority of the players are literally sacrificing their entire armies to kill it.
The idea here, is to encourage community and team play
, but who receives the wilderness loot could be an issue, perhaps design it so that all the participants get something, and the alliance with the most scale of soldiers contributed would get a big bonus to funds and/or development.
Only one of these should spawn in each zone per specific time interval, but hopefully they would all simultaneously spawn in all 4 zones at the same time to discourage one overpowered alliance from going after all 4 of them one by one and hogging them all for themselves, though this might still happen anyways.