Do you have to pay the mana cost for cards exiled with Muse Vessel?

Question

Muse Vessel reads as follows:

{3}, {T}: Target player exiles a card from their hand. Activate this ability only any time you could cast a sorcery.

{1}: Choose a card exiled with Muse Vessel. You may play that card this turn.

If the card exiled is a nonland card, do I have to pay its mana cost?

Answer 1

Yes, you do.

From the comprehensive rules (emphasis mine):

701.13b To play a card means to play that card as a land or to cast that card as a spell, whichever is appropriate.

701.4a To cast a spell is to take it from the zone it’s in (usually the hand), put it on the stack, and pay its costs, so that it will eventually resolve and have its effect.

Muse Vessel lets you play the card, which equates to casting a spell, but does not change the requirement to pay the cost for the spell.

Answer 2

First of all, to play a card is to play the card as a land or cast it as a spell.^{[CR 701.13b]}

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The words "play" and "cast" are used in three different, yet confusingly similar ways.

• "You may (play|cast) {something} {condition}."

  For example,

  A player may cast an instant spell any time they have priority.

  A player may cast a noninstant spell during their main phase any time they have priority and the stack is empty.

  These are found in the rules. These give you permission to play or cast a card (or copy thereof) at certain points in the game.

• "You may (play|cast) {something} [{alternative cost}]."

  This is an (optional) instruction to play or cast the card (or copy thereof) immediately.

  The fact that you don't have priority and that the stack isn't empty is irrelevant.

  These often provide an alternative cost (e.g. "without paying its mana cost") which replaces the mana cost of the card. Keep in mind that additional costs, cost increases and cost decreases are still applied when an alternative cost is used.

• "You may (play|cast) {something} [{alternative cost}] ({duration}|from {zone})."

  For example,

  You may play that card this turn.

  You may cast this card from your graveyard

  These alter which cards (or copy thereof) can be played or cast when you have permission to play or cast a card.

  They don't give you permission to play or cast a card.

  They don't instruct you to play or cast a card.

  They may alter the mana cost, but only if explicitly stated.

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Muse Vessel's ability uses the third of the above template. It simply allows you to play the card from exile as if it was in your hand until the end of turn. That's it.

• You still need to have priority to play it.
• The stack must still be empty unless its an instant.
• If it's cast as a spell, you must still pay its casting cost (including its mana cost, unless something provides an alternative cost).