Unlike cards such as Athreos, God of Passage, Outpost Siege triggers whenever a creature you control leaves the battlefield, not just when it dies, so it doesn’t matter if your opponent’s removal options are bounce, exile, or anything else! Outpost Siege will even trigger if all your permanents are nuked at once, such as with Perilous Vault. When the game goes to check whether any leaves-the-battlefield triggers need to go onto the stack, it “looks back in time” to see what the game state was like immediately before all your stuff left the battlefield; and since there’s an Outpost Siege there ready to be fired off, it’ll give you one trigger for each creature that met its unfortunate demise.
Today’s Rules Tip written by Jen Wong