If I reveal a land with Daxos of Meletis, can I play it?

Question

What happens if my Daxos of Meletis deals combat damage to a player, and the card revealed by that player is a land? Am I able to play that land or does nothing happen, because Daxos's ability is worded as "you may cast" that card and you don't cast lands.

Answer 1

The land is exiled and you gain 0 life. You may not play the land, because as you point out, the card says "cast" not "play":

[...] Whenever Daxos of Meletis deals combat damage to a player, exile the top card of that player's library. You gain life equal to that card's converted mana cost. Until end of turn, you may cast that card and you may spend mana as though it were mana of any color to cast it.

[CR601]. Casting Spells

601.1. Previously, the action of casting a spell, or casting a card as a spell, was referred to on cards as "playing" that spell or that card. Cards that were printed with that text have received errata in the Oracle card reference so they now refer to "casting" that spell or that card.

601.1a Some effects still refer to "playing" a card. "Playing a card" means playing that card as a land or casting that card as a spell, whichever is appropriate.

Djinn of Wishes and Intet, the Dreamer allow you to play exiled lands, Daxos does not.

The CR define what you can do in MtG, since no rule exists for Casting a Land, you cannot do it. Additionally, rules exist for cards that share the land type and an indication that lands are not spells (about the closest you will get that lands aren't spells).

305.9. If an object is both a land and another card type, it can be played only as a land. It can’t be cast as a spell.

505.5b During either main phase, the active player may play one land [...] Neither the land nor the action of playing the land is a spell or ability.

Answer 2

You cannot play the land, because Daxos only allows you to "cast" the card. The land will still be exiled; and it will simply stay in exile.

601.1a Some effects still refer to "playing" a card. "Playing a card" means playing that card as a land or casting that card as a spell, whichever is appropriate.

601.2. To cast a spell is to take it from where it is (usually the hand), put it on the stack, and pay its costs, so that it will eventually resolve and have its effect.

You can see in 601.2, "casting" specifically means to put it on the stack, which you do not do when playing a land.

Also note cards like Djinn of Wishes, which allow you to play a revealed card, as opposed to allowing you to cast a revealed card. That's the wording needed to allow you to play a land.

Answer 3

The land will be permanently exiled. Specifically,

1. You will exile the card.
2. You will gain zero life, which is to say you won't gain any life. Abilities that trigger when you gain life won't trigger^{[CR 118.9]}.
3. You cannot cast the land because it has an unpayable mana cost^{[CR 117.6, 601.2e,g]}. As such, it will stay exiled until the end of the game.

If Daxos of Meletis instructed you to play the card, that would be a different story. To play card is either to play it as a land or to cast it as a spell. You would be able to put the card on the battlefield for free if it's your turn and if you haven't already played a land that turn. It would count towards your limit of one land per turn.

If Daxos of Meletis instructed you to put the card on the battlefield, that would be a different story too. The card would immediately be moved directly from your hand to the battlefield. This wouldn't count towards your limit of one land per turn.

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Interestingly, there's no rule forbidding casting a land^[1]. MTG will simply never let you do it.

1. Land cards, as printed, have an unpayable mana cost, so they can't be cast.

2. What if the land's mana cost was replaced?

   Cards that replace the mana cost (e.g. "you may cast [card or copy] without paying its mana cost") will specifically exclude land cards. (e.g. Counterlash).

3. What if a card with a mana cost gains the land type?

   There's a rule specifically excluding these from being cast^{[CR 305.9]}.

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Notes

1. GendoIkari claims the rules say a land can never be a spell, but I believe he's misreading a rule^{[CR 305.1]}. 305.1 describes what happens when playing a land as a land. The land is not placed on the stack when playing it as a land, so the land is never a spell when playing it as a land. That doesn't mean it can't go on the stack at other times. That doesn't mean it can't be a spell at other times. But he thinks it does. He's right they can't, but not because of 305.1.

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Referenced Rules

118.9. Some triggered abilities are written, “Whenever [a player] gains life, . . . .” Such abilities are treated as though they are written, “Whenever a source causes [a player] to gain life, . . . .” If a player gains 0 life, no life gain event has occurred, and these abilities won’t trigger.

117.6. Some mana costs contain no mana symbols. This represents an unpayable cost. [...]

601.2. [...] Casting a spell follows the steps listed below, in order. [...]

601.2e The player determines the total cost of the spell. Usually this is just the mana cost. [...]

601.2g The player pays the total cost in any order. Partial payments are not allowed. Unpayable costs can’t be paid.

305.9. If an object is both a land and another card type, it can be played only as a land. It can’t be cast as a spell.

305.1. A player who has priority may play a land card from his or her hand during a main phase of his or her turn when the stack is empty. Playing a land is a special action; it doesn’t use the stack (see rule 115). Rather, the player simply puts the land onto the battlefield. Since the land doesn’t go on the stack, it is never a spell, and players can’t respond to it with instants or activated abilities.