The Wizards rules QA forum had a thread (you can read the original if you want), with the following question: When a Banisher Priest or Colossal Whale leaves the battlefield, is there ever a point in the game where neither it nor the creature it exiled is on the battlefield, for the purposes of state triggers?

The forum regulars are pretty much split down the middle, we'd appreciate an official ruling.

Yes, there is such a moment.

Basically, the game needs to know that Banisher Priest is gone in order to move whatever it was exiling. If a player controls Porphyry Nodes and Banisher Priest exiling a creature, and no other creatures are on the battlefield, detroying Banisher Priest will trigger Porphyry Nodes.

Daniel Kitachewsky
L3, Paris, France
Rules NetRep