What do you think about a Event at the end of the Season.
Example a few Days lasting Demon Invasion of OG/SW if the demons are able to Conquer our capital citys we lose and have to retreat get a few quests if we win we get a few quest to shut down some portals and celebrate.
And depending of the outcome the players of a server get a different blizzard art style video.
An Instanced raid of OG/SW after a certain time the winning faction claims the city with new NPC and get a few quest, the losing faction has to retreat and get a few quests aswell.
Thanks to the fact we play on a seasonal server there a endles even world ending possibilitys.