Please explain 'The Stack' to me.

[DewMan001]

I've been playing Magic for a while now, and I still have no idea how this seemingly primary and core principle of the game works. Could someone please explain it to me in a simple fashion?

Thank you!!

[Kapol]

So... the stack is a thing. That does stuff.

Or, to put it better, the stack is where things happen. When you play a card, an effect happens, or basically anything that involves doing something, it goes onto the stack. The stack then pauses and waits to see if anyone else will do something. This is when you can do instant-speed things, but not sorcery-speed things. So if I play, say, a counter in response to you casting something, the order goes like this:

Your card being cast goes onto the stack.
I respond with my counter. It goes on to the stack on top of your card.

The way the stack resolves cards is from the top down. So my counter will resolve first since it's on top. Now, if you countered my counter, then your counter goes on the stack above mine. It then resolves first. Normally you can do this until nobody casts anything, though there are some cards that can stop others from putting things onto the stack after it (such as split-second).

Does that help?

[Utilitarian]

How I came to understand the stack:

Whenever you do a thing, your opponent has a chance to respond to it via any kind of instant speed ability or spell

Thus, spells frequently are "played" but not yet "resolved"

When they are in this state, they live on the stack

-I cast a spell and pass priority to my opponent

Stack:
1.) My Spell

-My opponent responds to this spell with a counterspell and passed priority to me

Stack:

1.) My Spell
2.) My Opponent's Counterspell

-I'm annoyed at my opponent so I decide to dome him with a Lightning Bolt, and pass priority

Stack:

1.) My Spell
2.) My Opponent's Counterspell
3.) My Bolt

-My opponent doesn't have a response here, so things start resolving. The stack resolves the most recently cast spell first and then works backwards (If you think of it as a physical stack of spells, where the most recent spell is on top, and then they resolve from the top down to the bottom(

first, my bolt hits the opponent
second, my opponent's counterspell stops my original spell
third, my spell doesn't happen because it got countered

[DewMan001]

I think so. So, if I may take a moment to see if I've got this right, it's sort of like an ordered to-do list of things. Let's say a bring out a Gore-House Chainwalker and you, in response, Lightning Bolt it. The stack would look something like this?

Bolt on chainwalker

Chainwalker is summoned[[/list]

Right?

[Dominic Appleguard]

Well, no.

Think of the stack as though you were physically playing cards on top of each other, like a literal stack. Until each player stops casting spells or abilities, nothing on that pile will actually happen.

So, if you cast Lightning Bolt while the Chainwalker is on the stack, you can't hit the Chainwalker with it because it doesn't exist yet. If you did cast the Bolt, it would hit first; let's say you targeted your opponent's Dead Reveler instead. Then, once the Reveler is dead, the Chainwalker would come into existence.

If you want the creature dead, let it resolve, then Bolt it. If you're paying a blue deck with Counterspell, that's when you hit creatures while they are on the stack and still targetable as a "spell".


Another useful way to think about the stack is to think about why it exists. Magic is a complicated game, so if the rules allowed for many things to happen "simultaneously" then things would rapidly become enormously confusing. Instead, whatever was cast most recently is the most potent effect, because this system rewards players for thinking ahead by leaving mana open and holding onto their tricks.

Also if the stack didn't work this way counterspells would suck.

[Volafortis]

No, because the creature needs to resolve before it can be targeted, unless it's being targeted as a spell while on the stack.

Okay, so the way that Magic works as a game largely focuses around two things; the stack, and priority.

The stack is exactly what the name says it is, it's a Last-In-First-Out arrangement for resolving spells and abilities.

All spells (not lands) and all abilities except mana abilities use the stack.

Anything that is "instant speed" (Instants, things with flash, activated abilities) can be done "in response" to something on the stack (provided what you're doing is legal). This puts the spell or ability on "top" of the stack.

"Sorcery speed" spells and abilities can only be cast during your main phase when there are no spells on the stack.

Lands have special rules governing when they can be played and don't use the stack.

Mana abilities are defined as an ability which meets this criteria:

406. Mana Abilities

406.1. A mana ability is either (a) an activated ability without a target that could put mana into a player’s mana pool when it resolves or (b) a triggered ability without a target that triggers from a mana ability and could produce additional mana. A mana ability can generate other effects at the same time it produces mana.
406.2. Spells that put mana into a player’s mana pool aren’t mana abilities. They’re played and resolved exactly like any other spells.
406.3. A mana ability remains a mana ability even if the game state doesn’t allow it to produce mana.
406.4. A mana ability can be activated or triggered. Mana abilities are played and resolved like other abilities, but they don’t go on the stack, so they can’t be countered or responded to. See rule 411, “Playing Mana Abilities,” and rule 408.2, “Actions That Don’t Use the Stack.”
406.5. Abilities that produce mana but trigger from events other than playing mana abilities do use the stack. So do abilities that don't produce mana but trigger on playing mana abilities.
406.6. If a mana ability would produce one or more mana of an undefined type, it produces no mana instead.
Example: Meteor Crater has the ability “Tap: Choose a color of a permanent you control. Add one mana of that color to your mana pool.” If you control no colored permanents, playing Meteor Crater’s mana ability produces no mana.
406.7. Some abilities produce mana based on the type of mana another permanent or permanents could produce. The type of mana a permanent “could produce” at any time includes any type of mana that an ability of that permanent would generate if the ability were to resolve at that time, taking into account any applicable replacement effects in any possible order. Ignore whether any costs of the ability couldn’t be paid. If that permanent wouldn’t produce any mana under these conditions, or no type of mana can be defined this way, there’s no type of mana it could produce.
Example: Exotic Orchard has the ability “Tap: Add to your mana pool one mana of any color that a land an opponent controls could produce.” If your opponent controls no lands, playing Exotic Orchard’s mana ability will produce no mana. The same is true if you and your opponent each control no lands other than Exotic Orchards. However, if you control a Forest and an Exotic Orchard, and your opponent controls an Exotic Orchard, then each Exotic Orchard could produce G

So, we know what uses the stack, and when, but who can put spells/abilities on the stack?

This is where priority becomes important. Priority is a way to define the active player that may put spells on the stack.

When nothing is on the stack, the player whose turn it currently is is the active player, and has priority.

Now, here's where priority can get tricky to understand. When a player casts a spell, that spell goes on to the stack, and the current player still has priority. If the player wishes to resolve his or her spell, they must pass priority and give each opponent the opportunity to resolve.

When priority is passed, it passes around the table in turn order until each player has had an opportunity to respond. If priority makes a full pass around the table without anyone responding to the last spell cast, the spell resolves.

If someone responds, then priority makes another pass around the table to check again.

The player with priority is the only player that may put spells/abilities on the stack.

Example: A 4-player Free-for-all game with John, Rose, Dave, and Jade. The turn order is John>Rose>Dave>Jade

John is the active player, and it is his main phase. John casts Air Elemental. Air Elemental is then put on the stack, not the battlefield. John then passes priority to resolve his spell. Rose receives priority and passes it with no response. So does Dave, and so does Jade. Air Elemental then resolves, and enters the battlefield.

Rose has a Doom Blade in her hand that she wishes to use on the Air Elemental, but she needs priority to do so. If John casts another spell, she may respond by using Doom Blade on the Air Elemental, or she may wait for the current phase or step to end.

When a player ends his or her phase or step, priority is passed around the table for actions before the next phase actually begins. Note that the Untap step, Draw step, and Combat Damage step don't actually use priority or the stack for the associated actions (untapping, drawing, and damage resolution, respectively), so they can't be responded to.

So, let's say John ends his main phase.
Priority is then passed to Rose, who casts Doom Blade, targeting Air Elemental.
Rose passes priority to Dave who then casts a Lightning Bolt, targeting Jade.
Dave chooses to keep priority and casts Reverberate, targeting his own Lightning Bolt.
Dave then passes priority.
Jade passes priority with no action.
John receives priority again and casts Negate, targeting the Doom Blade.

So, our stack looks like this:

TOP (last in)
Negate (targeting Doom Blade, controlled by John)
Reverberate (targeting Lightning Bolt, controlled by Dave)
Lightning Bolt (targeting Jade, controlled by Dave)
Doom Blade (targeting Air Elemental, controlled by Rose)
BOTTOM (first in)

Assuming priority is then passed around the table with no further action, the stack would resolve as such:
Negate resolves, countering Doom Blade (which removes Doom Blade from the stack).
Reverberate resolves, putting a copy of Lightning Bolt on the stack. Dave chooses new targets for the copy. Priority goes around again.
The Lightning Bolt copy resolves.
Lightning Bolt resolves.

Note that Dave maintained priority to use Reverberate on his own Lightning Bolt. If he had passed priority and no one responded, the Lightning Bolt would have resolved and would no longer have been on the stack as a legal target for Reverberate.

Once a spell resolves, its actions are performed and the spell is put into the relevant zone that it goes to upon resolution. (Instants/Sorceries go to the graveyard, Artifacts, Creatures, Enchantments, and Planeswalkers go to the battlefield.)

Because permanents need to be targeted on the battlefield, you may not "respond" to the casting of a permanent by using removal on it. It must first resolve, and you must then receive priority to perform your action.

I've got a lot more I could say, but I'll end it there for now. Feel free to ask any further questions, so I can explain more fully what exactly you need help with.

[Utilitarian]

Not exactly.

See, if you cast your Chainwalker, the spell is on the stack

What this means is that the Chainwalker isn't summoned yet. The spell is still waiting to resolve so the creature doesn't yet exist

As a result you can't cast Bolt on it because it doesn't exist

For the order of events you describe to happen it would be

Cast Chainwalker, pass priority
Opponent passes priority
Chainwalker resolves, cast something else or pass priority
Opponent casts bolt on Chainwalker

[Kapol]

I think so. So, if I may take a moment to see if I've got this right, it's sort of like an ordered to-do list of things. Let's say a bring out a Gore-House Chainwalker and you, in response, Lightning Bolt it. The stack would look something like this?

Bolt on chainwalker

Chainwalker is summoned[[/list]

Right?

You're close, but not quite right. Until Chainwalker is off the stack, he's not actually on the field. A spell has to resolve before it happens. Which means that you're not going to be able to target the Chainwalker before it;s off the stack. So you couldn't target him with a lightning bolt with him on the stack.

Now, in a similar scenario, say your opponent plays Yeva's Forcemage targeting a creature to give it +2/+2. You, in response to the activation of the ability, bolt the targeted creature of the Forcemage's ability. Your bolt will resolve before the ability, killing the creature. (Also, as a small note, for Yeva's Forcemage's ability, you want to wait until after the Forcemage resolves. At that point, the Enter-The-Battlefield ability will trigger, giving you a chance to respond while that's on the stack.

[DewMan001]

So, to use the 'playing cards in a stack' as an example, card is played in the stack and then resolves (or goes where it's meant to go [graveyard, creatures row] on the table). So I wouldn't be able to bolt the Chainwalker because it hadn't resolved and gone in to it's appropriate place, yes? What sort of instants or spells could I use if the opponent's creature has not yet resolved?

[Utilitarian]

Really just spells that say "Counter target spell" and the like. so Essence Scatter, Dissipate, Syncopate, etc

*edit* Assuming you meant spells you could use to stop that creature from entering the battlefield. You can CAST any other kind of instant spell or activate most ability before the creature resolves, but most of them won't be able to stop that creature

[Volafortis]

I edited my earlier post with a ton of info, feel free to ask me more in-depth questions.

[Lord Hosk]

I dont know if this will help but...

When every card is played (spell is cast) it goes on the stack, every time.

Every other player, in turn order, then gets a chance to respond to the card (spell) on the stack with instants or abilities.

a card (spell) doesnt resolve until it leave the stack.

For the vast majority of the game a card enters and leaves the stack without anything happening. Every time you cast a creature, the spell goes on the stack, then the creature goes on the battlefield. But since its rare that anyone responds you just assume that unless someone specifically says so, the card enters and leaves the stack simultaneously its easier to think about the stack not existing.

This shows up better on MTGO because every time you cast a spell it automatically stops and you have to click ok to pass the priority or cast a spell.

This isnt normally how you think about it because it is really complicated but here is a typical turn two for two people as it is FULLY in play. with a board state of Player one has two forest in play both tapped and player two has one mountain in play untapped.

Player 1 untaps forests
Player 1 passes priority
Player 2 passes priority
Player 1 performs upkeep
Player 1 passes priority
Player 2 passes priority
Player 1 draws a card
Player 1 passes priority
Player 2 passes priority
Player one enters main phase one and chooses to tap one forest
Player 1 passes priority
Player 2 passes priority
Player one Taps a second forest
Player 1 passes priority
Player 2 passes priority
Player one casts Deadly Recluse
Deadly recluse enters the stack
Player 1 passes priority
Player 2 passes priority
Deadly recluse enters the battlefield
Player 1 passes priority
Player 2 passes priority
Player one enters Combat phase
Player 1 passes priority
Player 2 passes priority
Player one chooses not to declare attackers
Player 1 passes priority
Player 2 passes priority
Player one does no combat damage
Player 1 passes priority
Player 2 passes priority
Both players check to see if damage dealt exceeds creature toughness
Player 1 passes priority
Player 2 passes priority
Player one enters second main phase
Player 1 passes priority
Player 2 passes priority
Player one Plays a forest
Forest enters the stack
Player 1 passes priority
Player 2 passes priority
Forest enters the battlefield
Player 1 passes priority
Player two taps one mountain
Player 2 passes priority
Player 1 passes priority
Player Two casts shock targeting player ones deadly recluse
Shock enters the stack
Player 2 passes priority
Player 1 passes priority
Shock resolves dealing two damage to player ones deadly recluse
Both players check creatures for damage to see if they exceeds creature toughness
Player one places deadly recluse into the graveyard
Player 2 passes priority
Player one enters end phase
Player 1 passes priority
Player 2 passes priority

Player two enters untap step...


Also in between each thing I listed is a static check which among other things includes Both players check to see if damage dealt exceeds creature toughness, and has either player lost enough life to lose the game.

All that to say, "player one tapped to forest, played a deadly recluse, player two tapped a mountain and killed it, player one played a forest."

You can see why the stack and priorities are assumed to not exist unless you specifically want to interact with them, which can get tricky.

[Utilitarian]

Man. Ways to troll #8824: Manually list every priority pass and ask for every priority pass from your opponent when playing in face to face magic. Wow.

[Volafortis]

@Lord Hosk
You're wrong. Playing land and using mana abilities don't use the stack. I explain a lot of it in my post.

And now you understand why Wizards is wary of all the rules nightmares caused by printing more Land Creatures like Dryad Arbor.

The actual result there is:
Player 1 enters Beginning Phase
Player 1 Untap Step
Player 1 enters Upkeep
Player 1 passes priority
Player 2 passes priority
Player 1 Draw Step
Player one enters main phase one
Player 1 taps a forest (Add G as a mana ability)
Player 1 Taps a second forest (Add G as a mana ability)
Player 1 casts Deadly Recluse
Deadly recluse enters the stack
Player 1 passes priority
Player 2 passes priority
Deadly recluse enters the battlefield
Player 1 passes priority
Player 2 passes priority
Player one enters Combat phase (Declare Attacks step)
Player one chooses not to declare attackers
Player 1 passes priority
Player 2 passes priority
Declare Blocks step is entered. Since no were made, no blocks may be declared.
Player 1 passes priority
Player 2 passes priority
Enter Combat Damage Step
No Combat Damage has been assigned
Player 1 passes priority
Player 2 passes priority
Player 1 enters second main phase
Player 1 Plays a forest (It doesn't use the stack, it enters the battlefield as a special action.)
Player 1 passes priority
Player 2 taps a mountain (Add R as a mana ability)
Player 2 casts shock targeting player ones deadly recluse
Shock enters the stack
Player 2 passes priority
Player 1 passes priority
Shock resolves dealing two damage to player ones deadly recluse
Both players check creatures for damage to see if they exceeds creature toughness
Player one places deadly recluse into the graveyard
Player 2 passes priority
Player 1 enters end phase
Player 1 passes priority
Player 2 passes priority

Player 2's turn...

So it isn't as nuts as you suggest.

[Dominic Appleguard]

So, to use the 'playing cards in a stack' as an example, card is played in the stack and then resolves (or goes where it's meant to go [graveyard, creatures row] on the table). So I wouldn't be able to bolt the Chainwalker because it hadn't resolved and gone in to it's appropriate place, yes? What sort of instants or spells could I use if the opponent's creature has not yet resolved?

Counterspells have already been mentioned.

There are also some fancy effects that obliterate the stack entirely.

[Volafortis]

However, if you want to list all of the State-based Action checks, Imagine the phrase "Check State-based Actions" between every single line of that whole mess.

These are the state based actions, by the way:

704.5a If a player has 0 or less life, he or she loses the game.
704.5b If a player attempted to draw a card from a library with no cards in it since the last time state-based actions were checked, he or she loses the game.
704.5c If a player has ten or more poison counters, he or she loses the game. Ignore this rule in Two-Headed Giant games; see rule 704.5u instead.
704.5d If a token is phased out, or is in a zone other than the battlefield, it ceases to exist.
704.5e If a copy of a spell is in a zone other than the stack, it ceases to exist. If a copy of a card is in any zone other than the stack or the battlefield, it ceases to exist.
704.5f If a creature has toughness 0 or less, it's put into its owner's graveyard. Regeneration can't replace this event.
704.5g If a creature has toughness greater than 0, and the total damage marked on it is greater than or equal to its toughness, that creature has been dealt lethal damage and is destroyed. Regeneration can replace this event.
704.5h If a creature has toughness greater than 0, and it's been dealt damage by a source with deathtouch since the last time state-based actions were checked, that creature is destroyed. Regeneration can replace this event.
704.5i If a planeswalker has loyalty 0, it's put into its owner's graveyard.
704.5j If two or more planeswalkers that share a planeswalker type are on the battlefield, all are put into their owners' graveyards. This is called the "planeswalker uniqueness rule."
704.5k If two or more legendary permanents with the same name are on the battlefield, all are put into their owners' graveyards. This is called the "legend rule". If only one of those permanents is legendary, this rule doesn't apply.
704.5m If two or more permanents have the supertype world, all except the one that has been a permanent with the world supertype on the battlefield for the shortest amount of time are put into their owners' graveyards. In the event of a tie for the shortest amount of time, all are put into their owners' graveyards. This is called the "world rule."
704.5n If an Aura is attached to an illegal object or player, or is not attached to an object or player, that Aura is put into its owner's graveyard.
704.5p If an Equipment or Fortification is attached to an illegal permanent, it becomes unattached from that permanent. It remains on the battlefield.
704.5q If a creature is attached to an object or player, it becomes unattached and remains on the battlefield. Similarly, if a permanent that's neither an Aura, an Equipment, nor a Fortification is attached to an object or player, it becomes unattached and remains on the battlefield.
704.5r If a permanent has both a +1/+1 counter and a -1/-1 counter on it, N +1/+1 and N -1/-1 counters are removed from it, where N is the smaller of the number of +1/+1 and -1/-1 counters on it.
704.5s If a permanent with an ability that says it can't have more than N counters of a certain kind on it has more than N counters of that kind on it, all but N of those counters are removed from it.
704.5t In a Two-Headed Giant game, if a team has 0 or less life, that team loses the game. See rule 810, "Two-Headed Giant Variant."
704.5u In a Two-Headed Giant game, if a team has fifteen or more poison counters, that team loses the game. See rule 810, "Two-Headed Giant Variant."
704.5v In a Commander game, a player that's been dealt 21 or more combat damage by the same commander over the course of the game loses the game. See rule 903, "Commander."
704.5w In an Archenemy game, if a non-ongoing scheme card is face up in the command zone, and it isn't the source of a triggered ability that has triggered but not yet left the stack, that scheme card is turned face down and put on the bottom of its owner's scheme deck. See rule 904, "Archenemy."

[phlip]

The stack makes a lot more sense when you realise what it's for. The point is that we want to make it possible that I cast a spell, then you cast a spell in response, and yours happens first. I cast Murder, you cast Unsummon to save your guy. You cast a small creature, I cast Devour Flesh in response so you need to sacrifice your big creature on the table, rather than the small creature that hasn't resolved yet. And so on.
We want it to be like this because the alternative, that if I cast a spell then you cast a spell, and mine happens first, means that doing things "in response" doesn't do anything, and things just happen in the order they're cast. Takes a lot of the complexity out of the game, as things like counterspells, tricks, saving/protection spells, etc no longer work. Like, if I have a 2/2, you have a Lightning Bolt and I have a Giant Growth, then if you bolt my guy, I can't save it. In order to save it, I'd have to cast the Giant Growth first, in which case you just wouldn't bolt it, and would wait until next turn. Cards like Mizzium Skin wouldn't exist (or would be much less useful). Counterspells just wouldn't work.

So, we want some last-in-first-out order to spells being cast "in response" to each other. Ye Olde Magicke did this by grouping spells into "batches" - all spells/abilities you each cast get held together, until neither player wants to cast any more, and then the batch is resolved, LIFO. And then the next batch starts. This system turned out to be pretty inflexible, though... once any of the spells in the batch are resolving, they all do, before you get a chance to do anything else. The Stack is basically an extension of this to make it so that you can cast a spell, then cast another spell in response, let that second spell resolve, and still have the ability to cast spells after the second spell has resolved but before the first spell resolves.
What used to be "the current batch being built" became "the current stack", and instead of everything resolving in one hit, rather the top object on the stack gets popped off and resolves, one at a time.

Incidentally: both Lord Hosk and Volafortis's big lists of priority passes are wrong... neither of them even managed to make it out of the Beginning phase without an error (Hosk has priority passes in the Untap step, which don't happen. Volafortis misses priority passes in the Draw step, which do happen). I'm not going to try to make a list myself, as I'm sure I'd get it wrong, too. There's a reason a lot of this is shortcutted through in actual play.
But if you play Magic Online, try this as an experiment: put a stop on every single step you can, and note every time it offers for you to "cast spells or activate abilities" and you hit OK or F2. That's you passing priority.

[Volafortis]

Volafortis misses priority passes in the Draw step, which do happen). I'm not going to try to make a list myself, as I'm sure I'd get it wrong, too. There's a reason a lot of this is shortcutted through in actual play.

Gah, I had a feeling I'd missed some. And I even play Sylvan Library in Maverick, so I really should've remembered those. When I said that Untap, Draw, and Damage don't use the stack, I actually meant the actions that occur in those steps, untapping, drawing, and damage, none of which use the stack, although Combat Damage used to.

But yeah... it's a ton of stuff and really only should be mentioned if it's relevant, such as direct damage to planeswalkers, Infernal Tutor and then cracking Lion's Eye Diamond in response, Reverberate, etc...

Point is, it's a major part of magic that most players don't even know exists because it works pretty intuitively. High-level play shenanigans aside, most players can get by without understanding the complete ins and outs of the stack and priority, as long as they have the basic fundamentals understood.

[Del]

What sort of instants or spells could I use if the opponent's creature has not yet resolved?

The stack also matters for using activated abilities, and manipulating the effect of certain triggers like enters play abilities.

Super long example:

You are at 2 life.
You have a prodigal sorceror on the table untapped and ready for action, and a doomblade in your hand.
Opponent has a single 1/1 creature on the table, and he casts a foundry champion (when it enters play it deals damage equal to the number of creatures he controls to a target).

Stack
1) The cast (but not yet resolved) champion 'starts' the stack.
2) You ping the 1/1 with your prodigal sorceror, and pass priority back.
3) He has a chance to respond now, and casts a giant growth on his 1/1, and passes priority.

If the stack would end here (with you both passing priority), then the order goes backwards.
Giant growth buffs the guy, you ping him for one which is not enough damage to kill him now, and then the foundry champion resolves, doing two damage to a target (enough to kill you).

if the stack were to proceed, you could go
4) You doomblade the 1/1 and pass priority
5) He passes priority
6) You pass priority

Traveling backwards now, the doomblade kills the the 1/1 off the table to the graveyard. The Giant Growth no longer has a valid target (fizzles). The Prodigal Sorceror no longer has a valid target (activated ability fizzles). Stack ends. Foundry Champion resolves and it checks for the number of creatures its controller has in play (just one now, it). It deals just 1 damage to a target now, which is no longer enough to kill you (since you were at 2).

I am sure there's some complexities and nuances that I missed when it comes to wording, but that's an example of when you might want to pre-empt something using the stack.