This is a TOP Priority!

NOTE: GoT Spoilers (Kinda?) up to S6E9

Priority is something that I think confuses a lot of players.  Usually, priority seems to be encountered midway through the Magic learning curve.  A period where most of the basic rules (Attacking, Blocking, The Stack, Mana Costs, Ordering Spells)  have been learned and you're beginning to learn more advanced ones.

Unfortunately, the description given to Instants is spells that "can be play at any time."  While a good description to a newbie, runs counter to learning about priority.  The best description of Instants I believe is: Spells that can be cast "in response to" spells/abilities put on the stack or to changes in steps/phases.  

Priority is simply the order which people cast spells during turns.  There is an active player (the player's who turn it is) and everyone else (in turn order).  The active player starts with priority and either casts a spell or passes priority.  After that, each player in turn order receives priority.  This occurs for spells and the changing of phases and steps.  If all players pass priority the spell on the top of the stack resolves.  After this priority is again passed and the process repeats.  

During every turn there are at least a dozen passes of priority.  Where are all of these passes?  Why isn't  a single turn in the game not 5 minutes long?  This is generally because the actual action of passing priority and moving to different steps is often skipped less competitive games.  However on a competitive level you hear things like "Response?"  "Holding priority." "In response to that."  "On your upkeep"

It is also good to note that even though the actual act of passing priority and moving to different steps is often skipped for the sake of time and fluidity these actions still technically occur.

Exceptions

As with all rules there are exceptions to the rule.  In this case this primarily involves two kinds of actions:  Mana abilities and special actions.  In these cases these actions don't use the stack and can't be responded to.

Mana abilities are defined as an ability that:

• Doesn't have a target

• Could put mana in a player's mana pool

• Is not a loyalty (Planeswalker) ability.

Special Actions (that don't use the stack) are currently:

• Playing a land: This is relatively self explanatory

• Turning a face-down creature face up: These primarily involves paying Morph and Manifest costs to turn creatures face up often for added effects.

• Effects allowing players to take actions at a later time: Examples of this include  Quenchable Fire where you can pay a "U (a blue mana)" to prevent 3 additional damage and Dominating Lucid where you can "Pay to "U" to end the effect

• Static abilities allowing players to ignore an effect for a duration: The best examples of this are "soft lock" cards that tax a player before allowing them to perform certain actions.  Examples of this includes Leonin Arbiter where you can pay "2 (Colorless mana) to search and Damping Engine where you can sacrifice a permanent to play certain types of permanents.

• Suspending a card: This involves cards with the "Suspend" mechanic (Ancestral Vision)

• Rolling a planar die (In a Planechase game)

• Turning a face-down conspiracy face up (In a Conspiracy draft game)

This is why cards like Deathrite Shaman's and Xenagos' +1 ability are not mana abilities.  Specifically for Deathrite Shaman the ability saying "target"  

Holding Priority

There are certain occasions where holding priority is crucial and this needs to be stated as such "[Cast spell/activate ability] "Holding priority" [Continue putting abilities on the stack]"  Keep in mind two things with this:

1) Putting additional spell/abilites on the stack is reserved for instant speed spells and abilities.  This is because by their definition sorcery speed spells/abilites means the stack must be clear in order for them to be put on the stack (in addition to being during your main phases etc)

2) This does not mean that your spells/abilities can't be countered.  You're merely putting them all on the stack at once.  Your opponents have the opprotunity to respond after each spell/ability resolves.  (This is especially relevant to questions involving spells with Split Second like Krosan Grip which does not make other spells on the stack uncounterable)

Some examples of holding priority:

• Casting Armageddon, holding priority, casting Boros Charm (Your permanents are indestructible this turn mode) 
• Discarding a land to Borborygmos Enraged's ability and repeating this X times.

Not Holding Priority

There are certain circumstances where you actually don't want to hold priority.  An example of this is using Scavenging Ooze in the face of an opponent's Lightning Bolt.  In this case you want to let each exile trigger resolve one at a time so you can then respond with another exile activation in response to a Lightning Bolt should your opponent choose to bolt it.  If you tap out putting all the exile triggers on the stack at once an opponent can then respond by Bolting the Ooze before any of its abilities resolve.

Sac'ing permanents: Why can't you destroy sac'd permanents?

Often a confusing instance is when players attempt to kill a creature (or other permanents) to prevent their opponent from sacrificing it and are told that they can't.  In these cases the cost of putting the ability on the stack is the creature being sacrificed.  The way to tell the difference between the "cost" and the "effect" is the wording before and after the colon ":" or in the case of spells "As an additional cost to cast [Spell Name] do X"  If a permanent says "[Other costs], Sacrifice a creature:" then sacrificing is part of the cost.  However if the sacrificing of the creature comes after the colon then the creature can be killed as sacrificing it is not part of the cost.

Next Up

For my next article "Ogres have lairs Donkey!" I plan on going into detail about the dreaded topic of layering in Magic the Gathering.

Thanks for reading,
Sincerely, MTW

Acknowledgements and Sources

Nikolaus Steven Bonnay

Isaac King

Trevor Nunez

Cailean Bernard

Members of the MTG EDH COMMANDER Facebook group

Members of the Ask the Judge (MTG Rules Group) Facebook group