I did a quick survey of replacing cards and compiled this list of cards that would be affected if this were standard. (That is, a card effect that places a KNOWN CARD into a KNOWN POSITION that could be considered functionally Revealed)
Persistent and Durable cards are ignored (because they already do this) except when they perform an additional replacement. Cards that summon from a list of potential candidates are rightfully ignored.
Cards that place known cards into the opponent's hand:
Air nomad Harpy queen Wind witch Conscript army Cursed amulet Goblin intruder Elemental storm Desert traveler Thug Steelbeard Balrog CerberusCards that place known cards into your own hand:
Vampire lord (the selected card becoming Vampire)
Heresy Road to Tartarus Doppelganger (when targeting self to copy matching card)
Jungle river Flame obelisk Harvest fairy Hydra Mirror elemental Arcane tome Mason Forge master Steam golem HydromancerThe following keyword effects do the same:
- Holy
- Burning
- Flare Attack
- Horde, as previously discussed
- Dragon (if summoning a
Dragon egg, which the opponent would know by observing whether gem production was multiplied)
Special considerations:
- (I had originally discussed Dragon here before realizing that the effect is wholly transparent.)
-
Goblin regiment looks like it should be valid, but in a hidden game, the opponent would actually not know from which position the card was played. For example, playing it and having NEW cards in positions 2,5,7. It's possible that the replaced cards were in 2,5 or 2,7 or 5,7 with the remaining position being a normal draw. Therefore, it should be disqualified. That is, UNLESS we want to apply real-world logic to this and consider that in a match played across the table from one another, the opponent would actually watch the player play the card from its position. (Also, there's the possibility that the replaced Commons were revealed prior to the effect and the opponent does know precisely which positions were affected.)
I love obsessing over small details such as these.