An Vaal treasure temple named is focused completely on by incursion. "The central core of Incursion is that actions you create in the PoE currency past can affect the present day," Chris Wilson, lead writer at programmer 

Grinding Gear Games tells me. 

No one knows where to find it, however a new character named Alva Valai has about the best way to find its location, a theory. As players enter each new area during a standard effort, they will encounter Alva. If you speak to her, she'll offer to use as it existed in the past these stones to send one to the temple. As it's in the present, in doing so, you'll gradually show the location of the temple.

All these incursions send you into a random room within Buy Path of exile currency Atzoatl in the past at which you'll only have a limited period of time to kill all the monsters found there. You're going to have to move as quickly as 

you can, although each kill grants you time. 

A pub on the bottom of the display monitors your progress prior to killing every monster in the region and, once the timer runs out and you are sent back into the present, all the items you would have accumulated spill out in a single glorious fountain of loot.