Land or Enchantment. You can track it with a token, or dual faced/transform.
And again, someone said this is a "Standard" not 'standard' set. If this is a Standard format legal set, then it will not have some weird 2nd deck for dungeons to be drawn from. That is way too parasitic a mechanic.
If its NOT a Standard set, then all bets are off and it could be anything.
Modern Horizons 2 looks like it may as well be an Unset, that is trying to leverage massive amounts of nostalgia...but I'm not convinced its going to be what Modern needs in any capacity.
OK actually Obsidian Charmaw looks great for stomping on Tron, because that deck should have been killed off years ago.
EDIT: My google-fu is weak, but yeah AFR is indeed a Standard legal set. I dont see how Dungeon's are anything but a standard card type.
I also see Q4 has us returning to Innistrad, with a Werewolves vs Vampires theme. That is REALLY exciting, as I love the Werewolf cards.
