Gameplay Suggestion.

Black Gates that spawn (or come from ground) randomly as events in town areas with creatures from the underworld coming through and attacking players in town areas, Letting players in the area able to come to the towns rescue.
The creatures could attack the buildings as well setting them on fire or destroying walls etc, Players could put out the fires with water spells (or buckets), And when the Black Gate has been defeated players could use their crafting skills to fix the houses back up, I thought non combatant NPC's could be scripted to seek shelter inside houses etc.

Obviously this is a Guild wars 2 thing (or rift defiance etc) which I love, but I like the air of chaos in GW2 when it happens.

Cheers.

 

There should be a purpose to it. e.g. it's preventable if people are properly virtuous or whatever. So this is a way to motivate that town to work together to stay on top of something...or else