Basically,players above a certain tier can go to the nearest wormhole and travel to a galaxy that is under attack,full force,by ducks(or any other farm fowl that is slaughtered for meat).The galaxy is generated once,and may come under attack again.All planets have some preset missions that disappear when a pilot completes it.Wormhole systems exist for quick travel within the Galaxies.Shops in that Galaxy provide special discounts,or items not available during normal gameplay.All points and keys are tripled(because it’s a special event).When all missions are completed,all pilots can leave through he nearest wormhole to the main galaxy.
I’d love an Easter Egg in the galaxy on release that is basically a hard-coded version of the actual Solar System, myself (complete with Space Burger orbiting Earth). It’s in all the other CI games, after all.