If players ultimately failed to complete the invasion quest, there should be a zone-wide effect in line with the type of plane invading the zone. The effect shouldnt be too excessive in terms of duration but at the same time, be realistic and fun. Aim is to get players to be more actively involved in the invasion quests

Some examples.

Fire plane - zone-wide, one time off DOT that will kill(burn) everything in the zone or just some random deadly meteor shower.
Life plane - zone-wide DOT that drains life or a debuff that reduces healing up to 90% for 5 mins.
Death plane - zone-wide one time off sudden death.
Water plane - zone-wide rain with very reduced visibility or players get stuck in underwater status with the breath bar unless they move to higher ground.
Earth plane - zone-wide dust with very reduced visiblity or players suffer movement penalty for 5 mins.