I have two decks that can venture into the dungeon multiple times a turn I am wondering about the length of the ability for:
Runestone Caverns - Exile the top two cards of your library. You may play them.
Mad Wizard's Lair - Draw three cards and reveal them. You may cast one of them without paying its mana cost.
What is the window of opportunity for both of these? Do they have different windows? Is it only while the dungeon ability is on the stack? Is it until the end of turn? Is it forever (but only once: meaning if I cast lightning bolt from exile and it gets re-exiled I cannot recast it again, nor if it is one of the revealed three and I cast it for free, get it back to my hand with Archeomancer I cannot cast it for free again from my hand even though it was the chosen card)?
I ask because I had been both as an "until the end of turn" effect, but if it is shorter, it brings into question cast timings such as what if I get only permanent spells with any of these and the venturing occurred during combat, does it get around cast timing restrictions or did I essentially lose the top two cards of my library/not get a free spell?
I ran into the same issue yesterday at my FNM. Apparently those effects circumvent timing restrictions so you can in fact play The Tarrasque for free during combat thanks to your Planar Ally attack trigger activating Mad Wizard's Lair, and use your mana to play a removal spell after The Tarrasque resolves but before the declare blocker steps, and yes, I obviously won that game:p
Each room ability on a dungeon is a triggered ability that begins with "When you move your venture marker into this room, ...". For example, one of the rooms on Dungeon of the Mad Mage has the formal meaning: "When you move your venture marker into this room, exile the top two cards of your library. You may play them."
As such, "You may play them" is an effect of a triggered ability that doesn't specify a duration, so you choose whether to "play them" while the room ability is resolving, which is a moment that cards normally can't be played, not even instant spells (C.R. 608.2g, 117.1a). Notably:
You can play either or both of the two cards exiled this way (either or both, in view of a ruling for Chandra, Pyromaster). For example, you can cast a noninstant spell this way, and if it's your turn and you didn't play a land yet, you can play one land from among those cards.
You can play those cards only while the room ability is resolving, and not later (compare with Ornate Kanzashi and Commune with Lava), and you must pay all costs required, including the mana cost, for any spell you cast this way (C.R. 601.2f, 601.2h; compare with the last ability of Chandra and see also Harness the Storm). Any cards you don't play this way will remain in exile and you can't play them later.
In general, a card's type (such as instant or sorcery) doesn't impose a restriction on when a player can cast a spell (review C.R. 117.1a); examples of timing restrictions include those found in Aleatory, Savage Beating, or Teferi, Mage of Zhalfir.
I have two decks that can venture into the dungeon multiple times a turn I am wondering about the length of the ability for:
Runestone Caverns - Exile the top two cards of your library. You may play them.
Mad Wizard's Lair - Draw three cards and reveal them. You may cast one of them without paying its mana cost.
What is the window of opportunity for both of these? Do they have different windows? Is it only while the dungeon ability is on the stack? Is it until the end of turn? Is it forever (but only once: meaning if I cast lightning bolt from exile and it gets re-exiled I cannot recast it again, nor if it is one of the revealed three and I cast it for free, get it back to my hand with Archeomancer I cannot cast it for free again from my hand even though it was the chosen card)?
I ask because I had been both as an "until the end of turn" effect, but if it is shorter, it brings into question cast timings such as what if I get only permanent spells with any of these and the venturing occurred during combat, does it get around cast timing restrictions or did I essentially lose the top two cards of my library/not get a free spell?
Thank you in advance.
As such, "You may play them" is an effect of a triggered ability that doesn't specify a duration, so you choose whether to "play them" while the room ability is resolving, which is a moment that cards normally can't be played, not even instant spells (C.R. 608.2g, 117.1a). Notably:
In general, a card's type (such as instant or sorcery) doesn't impose a restriction on when a player can cast a spell (review C.R. 117.1a); examples of timing restrictions include those found in Aleatory, Savage Beating, or Teferi, Mage of Zhalfir.
See also this submission on Reddit, as well as this thread.