My friend just got his Pathfinder Adventure Card Game set and I watched him go through a solo game. One point that came up quite a few times was Summoned Monsters. When returning them to the box, my friend shuffled them into the monster deck every time.
I pondered this: is "returning to the box" the same as Banish? Banish does say "put it back into the box, shuffling it with the other cards of the same type".
As is, I find it somewhat strange because it can lead to what happened to us: getting 3 Specters in a row, which was a horrible thing for a character with no magic, in a situation where the summoned monster needs to be defeated to close the location (Brigandoom, Farmhouse).