Casting spells is one of the essential aspects of Magic: the Gathering. It’s something that every player does in nearly every game, and it generally occurs without issue. However, few Magic players know how casting a spell actually works from beginning to end. Knowing these minutia can help to understand a wide variety of otherwise-confusing situations, so I’m going to break it down for you. Let’s get into it!

So what does it mean to “cast a spell,” really? Let’s read what the comprehensive rules have to say:

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. Casting a spell includes proposal of the spell (rules 601.2a–d) and determination and payment of costs (rules 601.2f–h). To cast a spell, a player follows the steps listed below, in order. A player must be legally allowed to cast the spell to begin this process (see rule 601.3). If, at any point during the casting of a spell, a player is unable to comply with any of the steps listed below, the casting of the spell is illegal; the game returns to the moment before the casting of that spell was proposed (see rule 721, “Handling Illegal Actions”).

The first thing we learn here is that when players propose the casting of a spell, the card representing that spell is removed from the place it currently exists and goes onto the stack. What the rules refer to when they say the “steps listed below” are each very lengthy, in-depth descriptions. Here I have summarized the steps as a brief list before breaking them down:

Propose casting the spell, putting the card on top of the stack Announce choices for the spell (modes, alternative/additional costs, value of x, “splice onto” abilities, etc.)

Announce choice of target(s), if any

Choose division between targets if applicable

Determine if the proposed spell is legal to cast. If so, proceed, otherwise rewind the game to before the spell was proposed. Determine and pay the total cost of the proposed spell Calculate the mana cost based on proposed choices and current cost-altering effects

Activate desired mana abilities

Pay costs in any order desired. If costs are paid, proceed, otherwise rewind the game to before the spell was proposed.

The spell becomes “cast.” Effects that modify a spell “as it is cast” are applied, and abilities that trigger “when a spell is cast” trigger.

Start by Stacking

The first thing to note is that while a spell is being cast, it goes onto the stack and does not exist in any other zone (hand, graveyard, exile, etc.). This was highlighted recently when Squee, the Immortal was released into a Standard format with Ixalan’s Binding in it. If Squee is exiled with Ixalan’s Binding, can the exiled Squee be cast? Yes! No, unfortunately.

He’s immortal and confusing!

This is counter-intuitive: If we can’t cast spells with the same name as the exiled card, how can we cast the actual exiled card ? It’s because the game doesn’t check legality of a cast spell until after it has been put onto the stack. If Squee, the Immortal is exiled with Ixalan’s Binding, Squee’s owner can propose casting it and put it onto the stack. After Squee goes onto the stack, that’s when the rules check to see if casting Squee is legal. Since Squee, the Immortal is on the stack, it is no longer exiled with Ixalan’s Binding and since there is no exiled card, casting Squee is a legal action.

The previous paragraph used to be true, when Squee, the Immortal was first printed. However, the rules were changed specifically because these two cards together were not working as intended (many thanks to /u/KingSupernova for letting me know about this)! The crux of the change is that now, a spell is only legal to propose casting if decisions that are made while putting the spell onto the stack could change the attribute that would prevent the spell from being cast (see below for a good example). In this case, while attempting to cast Squee there is no decision we can make that would change the spell’s name (which is what’s stopping us from casting it), so we’re never allowed to put it on the stack.

I wonder if they knew they would have to restrict this thing instantly upon printing it

For an example of decisions that can change a spell’s attributes, players can use Mystic Forge to cast any card with morph as a face-down creature from the top of their library. Vesuvan Shapeshifter is not colorless, nor is it an artifact, but when a player decides to cast it as a face-down creature spell it goes face-down onto the stack and becomes a colorless 2/2 creature spell with no other attributes. That means that by the time the rules check it for legality, it’s not Vesuvan Shapeshifter at all; it’s just a nameless, colorless creature card, and that makes it a legal spell to cast with Mystic Forge.

Two cards, for the price of… two? But you cast one. For the price of one.

When proposing to cast a split card, we must choose which spell we are casting before we put it on the stack. In any zone but the stack, the game treats a split card as one card with all the attributes of both the spells that the card represents. On the stack, however, only the spell that is being cast is recognized. For instance, If we have Fire // Ice in our hand and we want to kill a pair of 1/1 creatures, we would propose that we are casting Fire and put it onto the stack. From that point until it resolves, the game treats the spell as though Ice does not exist; the spell on the stack is called Fire, and it’s a red instant that costs 1 and a red.

YOU MUST CHOOSE

The next step after putting our spell onto the stack is to make all the choices that spell requires. If that sounds vague, it’s because there are so many possible choices we might have to make that a list covering all of them would not be useful for any one situation.

It’s just so versatile

To cast Fiery Confluence, after we put it on the stack we need to choose which modes we want (and how many of each). Let’s say there are two artifacts that we want to destroy; we should choose the “Destroy target artifact” mode twice, then since there is one choice left to make let’s choose to deal 2 damage to each opponent. Once we announce these choices, we can choose the targets for the two instances of the “Destroy target artifact” mode.

“Did you do it?”

“Yes”

“What did it cost?”

“…Five mana”

When casting a spell using an alternative cost, that choice must be made before targets are chosen. For example, Fist of Suns gives us the option to pay an alternative cost instead of paying the spell’s mana cost. Commonly, players misuse alternate costs because they think that the ability changes the cost of the spell they are casting; the truth is that these abilities actually add a new, different cost that can be paid instead of the mana cost of the spell. For example, if we control Fist of Suns and we don’t want to pay full price to cast Elder Deep-Fiend, we can choose to pay for Fist of Suns or choose to sacrifice a creature and pay its emerge cost. We can’t say we’re going to pay WUBRG and sacrifice a creature, because Fist of Suns and emerge are two different alternative costs.

Abilities that say to cast something “without paying its mana cost” are also alternative costs, and as such they can’t be combined with other alternative costs. For example, if we cast a Maelstrom Wanderer and cascade into Crush of Tentacles, we won’t be able to cast it for its surge cost even though we’ve cast another spell this turn. Cascade says that you may cast the spell for the specific alternative cost of “without paying its mana cost” and since surge is another alternative cost, it can’t be used during a cascade.

Sometimes spells have additional costs that can or must be paid. Additional costs can be chosen even when casting a spell for an alternative cost! Note that if we are casting a spell without paying its mana cost, we will have to pay for any additional costs we choose to add. If we cascade into a Wolfbriar Elemental, for example, we can choose to cast it without paying its mana cost and choose to kick it any number of times. Just remember that when it comes time to pay costs, we will need to pay one green for each time we chose to kick it.

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Target Required?

Once those choices have been made, it’s time to choose targets for your spell (if necessary). If a spell calls for a certain number of targets, a valid object must be chosen for each of those targets or the spell can’t be cast.

Going back to our earlier example when we cast the Fire half of Fire // Ice, we need to choose one or two targets. As mentioned earlier, we want to choose our opponent’s two 1/1 creatures as the spell’s targets. The next step is to divide the spell’s effect between its targets: In this case we’d choose to divide the damage evenly, dealing 1 damage to each of the two creatures.

It’s important to note that when dividing the effects between a spell’s targets, at least one of the divided effect must go to each target. We can’t target two creatures with Fire, then deal 2 damage to one of them and no damage to the other; we would have to choose a single creature as the target in order to deal 2 damage to that creature.

Sanity Check

Obligatory “can’t even” joke

Once all our choices have been made and announced, the game checks whether that spell with those choices is legal to cast. The reason it’s handled this way is so that if a spell only becomes illegal after choices are made, it still gets caught by the check. For example, if our opponent controls Void Winnower and we cast a Fireball, the game waits until we’ve chosen a value for X to check if the converted mana cost is odd or even. If the spell is illegal, the game state is returned to just before the spell was proposed (see the section titled “Ctrl+Z” below). If the spell is legal, then it’s time to deal with costs.

Recalculating…

Before we can go about paying for our spell, we first need to determine how much it will cost. To determine a spell’s mana cost, we start with the mana cost or alternative cost we chose and add to it any additional costs we chose to add. Then we apply cost-modifying effects, if any exist, in any order we choose. Last, we apply any effects that change the total cost of a spell (a la Trinisphere).

If the spell had additional or alternative costs like sacrificing creatures or discarding cards, we need to note them as part of the spell’s total cost as well. Once all costs are accounted for, we have determined the “total cost” of the spell; this cost is now “locked in” as the amount we will pay, but it’s not quite time to pay yet!

We All Float Down Here

Mana abilities need to be activated before the cost-paying begins. The mana we will use to cast the spell needs to be in our mana pool before we can spend it, so this is the time to activate mana abilities. Mana abilities don’t require a player to have priority to use them, and they don’t use the stack. That makes them the only abilities that can be activated during the casting of a spell, because no player has priority while a spell is being cast. But what defines a “mana ability” exactly? Here’s what the comprehensive rules say:

605.1a An activated ability is a mana ability if it meets all of the following criteria: it doesn’t require a target (see rule 114.6), it could add mana to a player’s mana pool when it resolves, and it’s not a loyalty ability. (See rule 606, “Loyalty Abilities.”)

605.1b A triggered ability is a mana ability if it meets all of the following criteria: it doesn’t require a target (see rule 114.6), it triggers from the resolution of an activated mana ability (see rule 605.1a) or from mana being added to a player’s mana pool, and it could add mana to a player’s mana pool when it resolves.

Most mana abilities grant the ability to simply tap a permanent for mana. However, some mana abilities have other effects tied to them, and as such these abilities can trigger effects while a spell is being cast: For example, Ashnod’s Altar has a mana ability that requires us to sacrifice a creature. If we activate the ability while casting a spell, and that sacrifice triggers an ability, it won’t happen right away:

704.3. Whenever a player would get priority (see rule 116, “Timing and Priority”), the game checks for any of the listed conditions for state-based actions, then performs all applicable state-based actions simultaneously as a single event. If any state-based actions are performed as a result of a check, the check is repeated; otherwise all triggered abilities that are waiting to be put on the stack are put on the stack, then the check is repeated. Once no more state-based actions have been performed as the result of a check and no triggered abilities are waiting to be put on the stack, the appropriate player gets priority...

Triggered abilities don’t go onto the stack until a player would get priority, so the trigger will “wait” until the spell is finished being cast, then the ability will go onto the stack on top of the spell we were casting. If several abilities trigger while casting a spell, it doesn’t matter what order they trigger in; once we finish casting the spell, we get to put the triggers onto the stack in whatever order we want.

If activating a mana ability changes a value that would have affected the cost of the spell we’re casting, it does not change how much we have to pay. The cost has been “locked in” and it will not change until it’s paid. Here’s an example:

We control Etherium Sculptor and Ashnod’s Altar and we are casting a Darksteel Ingot for its mana cost. The spell’s mana cost is 3 generic, and Etherium Sculptor reduces its cost by 1 generic, so we determine that the total cost of the spell is 2 generic. Now that we have determined the total cost, it gets locked in; we can sacrifice Etherium Sculptor with Ashnod’s Altar for 2 mana and the spell’s cost will not increase.

Time to Pay Up

Once we have done our calculations and floated our mana, it’s time to pay the cost of the spell. Costs can be paid in any order, but once we start paying costs we can’t activate any more abilities, even mana abilities. If the spell is fully paid for, congratulations! We have completed the casting of the spell; if the spell has any values that are determined “as you cast” the spell, they are determined now. Any abilities that triggered while casting go onto the stack on top of the spell, then if any abilities trigger when the spell is cast, those abilities are put on top of the stack. Finally, once all triggers are on the stack, we get priority again. We can activate or cast anything that is instant-speed, but If we want our triggers or spell to resolve, we have to pass priority.

Ctrl+Z

If we are unable to pay for our spell for some reason, the spell is illegal. The game is “rewound,” returning to the point in time just before we proposed the spell that we failed to cast. Normally this just means returning the spell to the zone it was cast from and untapping the mana sources we tapped, but sometimes it’s a bit more complicated. For a better idea of when it gets tricky, let’s look at how the rules say to handle illegal actions:

721.1. If a player takes an illegal action or starts to take an action but can’t legally complete it, the entire action is reversed and any payments already made are canceled. No abilities trigger and no effects apply as a result of an undone action. If the action was casting a spell, the spell returns to the zone it came from. Each player may also reverse any legal mana abilities that player activated while making the illegal play, unless mana from those abilities or from any triggered mana abilities they caused to trigger was spent on another mana ability that wasn’t reversed. Players may not reverse actions that moved cards to a library, moved cards from a library to any zone other than the stack, caused a library to be shuffled, or caused cards from a library to be revealed. 721.2. When reversing illegal spells and abilities, the player who had priority retains it and may take another action or pass. The player may redo the reversed action in a legal way or take any other action allowed by the rules.

I think the marionettes might be a metaphor

For example, let’s say we control Marionette Master, Tolarian Academy, and three Treasure tokens. We sacrifice our treasures to add mana for a spell, which triggers Marionette Master‘s ability, but now we don’t control enough artifacts for Tolarian Academy to finish paying for our spell; we’re unable to pay for the spell fully. Since we never finished casting the spell, no player has gained priority, and therefore Marionette Master‘s ability was never put onto the stack. Similarly, tokens in the graveyard cease to exist as a state-based action, but state-based actions aren’t checked until a player would gain priority so our tokens still exist. To rewind the casting attempt we would return the Treasure tokens to the battlefield, lose the mana that they produced, and Marionette Master‘s triggered ability goes away before it reaches the stack. Once all of that is done, we regain priority and may proceed however we wish, most likely tapping Tolarian Academy first, then sacrificing our Treasures. As you can see, if everything about casting a spell is handled properly it isn’t difficult to undo illegal ones*. That is, except for a few edge cases…

*Reddit user /u/KingSupernova from the MTG Judge subreddit kindly informed me that this part of the comprehensive rules is overruled during competitive play by the tournament policy at whatever Rules Enforcement Level the tournament is being judged at.

Bob’s Favorite Thing: Wacky Stuff

Editor’s note: Headache warning ahead

There are some extreme edge cases for spell casting that are so weird, I just have to tell you about them. These edge cases involve two things: Mana abilities that you can’t undo, and spells that you can cast at weird times.

It’s, like, a deluxe mana ability

Selvala, Explorer Returned is a prime example of a mana ability that can’t be undone. As a reminder:

...Players may not reverse actions that moved cards to a library, moved cards from a library to any zone other than the stack, caused a library to be shuffled, or caused cards from a library to be revealed.

Selvala breaks two of these rules, revealing cards from libraries and causing players to draw cards (which moves cards from libraries to hands). It’s a mana ability, which means it can be used at any time and doesn’t use the stack, but once it’s activated it can never be undone. If we try to pay for a spell using Selvala’s ability but she doesn’t produce enough mana, the game state returns to how it was before we proposed the spell except for Selvala. She stays tapped, we keep the mana and life she gave us, and each player keeps the card they drew. It’s like Selvala looks into the future and changes the timeline, but she can’t undo what has already been done.

Surpriiiiiiiiiiiiiiiiiiise

Panglacial Wurm is notorious for creating weird interactions while casting spells. Its ability allows it to be cast while searching our library, which only happens during the resolution of a spell or ability. No player has priority while a spell or ability is resolving, which means that casting Panglacial Wurm from our library does not require priority! However, casting the Wurm is definitely not a mana ability, and therefore it still uses the stack. We can cast it like it has flash by activating a Evolving Wilds, for example, casting it during the resolution of the land’s ability. While the Evolving Wilds ability is resolving, it stays on top of the stack. Therefore, when we propose casting the Wurm, it goes on top of the stack under the Evolving Wilds ability, which is still currently resolving. Once it is successfully cast, we then finish resolving Evolving Wilds‘ ability. Once that ability is completely finished resolving, we put any triggered abilities from casting the Wurm or the land entering the battlefield onto the stack in any order. Then the Active Player (the player whose turn it is) gets priority.

Now let’s put the two together (plus a bonus): We control Selvala, Explorer Returned and Millikin. It’s our opponent’s turn, and they activate Field of Ruin targeting one of our lands. We let it begin to resolve, putting the destroyed land into the graveyard and start searching our library. At this time, we propose that we are going to cast Panglacial Wurm. If our opponent has not chosen their land yet, they cannot choose it until the Wurm is cast. If they have chosen, they can’t put it onto the battlefield yet because Field of Ruin‘s ability is simultaneous for each player and we have not chosen a land yet.

So we and our opponent are each searching our libraries, and we take Panglacial Wurm out and put it on the stack. There are no other choices to make, so the game checks if the Wurm is legal to cast: It is, because we are currently searching our library and that’s where the Wurm is being cast from. Now we determine the cost of the spell (in this situation it’s the full-price {5}{g}{g}), and start activating mana abilities. We tap lands for 4 mana, but unfortunately none of it is green and Selvala is our only available source of green mana. If we use her mana ability, we want to reveal a nonland card in order to get that green mana. Since each player is currently searching their library, we can see the order of cards in our library! However, searching a library does not allow a player to re-order the cards in it. For that, we can use Millikin! If the top card of our library is a land, we can activate Millikin because its ability is also a mana ability. That land on top of our library goes to our graveyard and we get one colorless mana. Now we can see that the top of our library is nonland, so we activate Selvala, Explorer Returned. We reveal the top card of our library, which we’ve made sure is nonland, and our opponent reveals the top of their library, which is… a land (sad trombone noise). We add one green and gain 1 life, then each player draws the top card of the library they’re currently searching.

Unfortunately, we have failed to obtain all the mana required to cast Panglacial Wurm. As a result, the Wurm goes back into our library (technically it goes back to exactly the position in the library it was cast from, but that isn’t really enforceable) and we are given the opportunity to undo mana abilities activated during the attempt. We can untap all the lands we tapped for the Wurm, but Selvala and Millikin remain tapped because they caused cards to move from a library to a different zone. When the rewind is completed (but before Field of Ruin continues resolving) we have an extra card in hand, one more life than before, and one colorless and one green in our mana pool. If we want to (and are real jerks) we can propose casting Panglacial Wurm again, however since we have no possible way to pay for it the result will be that we wind up right back here again, with no additional effects having happened. Eventually, each player will dig out a basic land, libraries will be shuffled, and that Selvala and Millikin mana will be lost. Better luck next time!

Whew

Well, that pretty much covers the basics. There’s plenty more where that came from, but I think I have spelled out (pun intended) everything you need to know for a basic understanding of “casting a spell” from beginning to end. Thanks for reading, and tune in next time when I cast Squee, the Immortal from exile after giving him madness with Falkenrath Gorger and Arcane Adaptation then discarding him and countering the madness trigger!