DDO Eberron Unlimited did the best interactive invasion I've ever played in an mmo, it was epic! Portals opening all over the usually safe city, players fighting hoards of demons trying to get through, innocent NPCs getting slaughtered left and right, and the city left with permanently ruined areas afterwards, the huge tent blown to bits and left in a state of semi-repair as the good folks tried to start rebuilding. Something like that would be amazing in eso.