The Visitor Event Guide/Discussion.

Credits to Dusk for explaining what he did for me:

It's best for an FP to go. Have the attackers attack red side, and let the FP Mist full yellow side. FP waits a bit after mist, and one Meteor clears entire yellow side. Convenient, but when I did it I was useless at bosses and even got 1 hit.

In fact, you can mist most of the maps in pq.

After you change dimensions the Poison mist dissapears (even if it was before the time runs out). What you can do is mist the yellow side, then wait until they're all posioned, go over to the red side, use fire demon on the mobs first to reset their resistances (since they're immune or atleast resistant to poisoning) and then poison them with mist.