Lesson 7 (Judge Classes)
Week 6 Recap
State Based Actions (Comp. Rules section 704)
Whenever a player would get 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.
- 1 Handling Triggered Abilities
- 1.1 Trigger Conditions
- 1.2 Placing Triggered Abilities on the Stack
- 1.3 Conditional Triggered Abilities
- 1.4 Optional Triggered Abilities
- 1.5 Zone-Change and Enters/Leaves-the-Battlefield Abilities
- 1.6 Delayed Triggered Abilities
- 1.7 Reflexive Triggered Abilities
- 1.8 Abilities Triggered by the Game State
- 2 Additional Resources
Handling Triggered Abilities
(Comprehensive Rules Section 603)
Triggered abilities have a trigger condition and an effect. They are written as “[trigger condition], [effect]”, and begin with the expression “When”, “Whenever” or “At”. They may also be expressed as “[When/Whenever/At] [trigger event], [effect]”.
Whenever a game event or game state matches a triggered ability’s trigger event, that ability automatically triggers. The ability doesn’t do anything at this point.
When a phase or step begins, all abilities that trigger “at the beginning of” that phase or step trigger. An ability triggers only once each time its trigger event occurs. However, it can trigger repeatedly if one event contains multiple occurrences.
Some trigger events use the word “becomes”; for example, “becomes attached” or “becomes blocked”. These trigger only at the time the named event happens. They don’t trigger if that state already exists or retrigger if it persists. An ability that triggers when a permanent “becomes tapped” or “becomes untapped” doesn’t trigger if the permanent enters the battlefield in that state.
If a triggered ability’s trigger condition is met, but the object with that triggered ability is at no time visible to all players, the ability does not trigger.
Because they are not cast or activated, triggered abilities can trigger even when it is not legal to cast spells or activate abilities.
Placing Triggered Abilities on the Stack
Once an ability has triggered, its controller puts it on the stack as an object that’s not a card the next time a player would receive priority.
- The ability becomes the topmost object on the stack.
- It has the text of the ability that created it, and no other characteristics.
- It remains on the stack until it’s countered, it resolves, a rule causes it to be removed from the stack, or an effect moves it elsewhere.
A triggered ability is controlled by the player who controlled its source at the time it triggered.
If multiple abilities have triggered since the last time a player received priority:
- If multiple abilities have triggered since the last time a player received priority, each player, in APNAP order (Active Player – Non Active Player), puts triggered abilities he or she controls on the stack. If a player has several abilities to put on the stack, that player can place them in the order of his or her choice.
- The game once again checks for and resolves state-based actions until none are performed.
- Abilities that triggered during this process go on the stack.
- This process repeats until no new state-based actions are performed and no abilities trigger.
- The appropriate player gets priority.
If a triggered ability is modal, its controller announces the mode choice when he or she puts the ability on the stack. If one of the modes would be illegal (due to an inability to choose legal targets, for example), that mode can’t be chosen. If no mode can be chosen, the ability is removed from the stack.
The remainder of the process for putting a triggered ability on the stack is identical to the process for casting a spell. If a choice is required when the triggered ability goes on the stack but no legal choices can be made for it, or if a rule or a continuous effect otherwise makes the ability illegal, the ability is simply removed from the stack.
Conditional Triggered Abilities
A triggered ability may read “When/Whenever/At [trigger event], if [condition], [effect]”.
The if [condition] part is a condition that must be fulfilled in addition to the trigger event for the ability to be put on the stack. When the trigger event occurs, the ability checks whether the stated condition is true. The ability triggers only if it is; otherwise it does nothing. If the ability triggers, it checks the stated condition again as it resolves. If the condition isn’t true at that time, the ability is removed from the stack and does nothing. Note that this mirrors the check for legal targets. This rule is referred to as the “intervening ‘if’ clause” rule. This rule only applies to an “if” that immediately follows a trigger condition.
In summary, the game verifies the condition twice:
- When it’s about to be put onto the stack
- When it’s about to resolve
Optional Triggered Abilities
Some triggered abilities’ effects are optional (they contain “may”, as in “At the beginning of your upkeep, you may draw a card”). These abilities go on the stack when they trigger, regardless of whether their controller intends to exercise the ability’s option or not.
The choice is made when the ability resolves. Likewise, triggered abilities that have an effect “unless” something is true or a player chooses to do something will go on the stack normally; the “unless” part of the ability is dealt with when the ability resolves.
Zone-Change and Enters/Leaves-the-Battlefield Abilities
Trigger events that involve objects changing zones are called “zone-change triggers.” Many abilities with zone-change triggers attempt to do something to that object after it changes zones. During resolution, these abilities look for the object in the zone that it moved to. If the object is unable to be found in the zone it went to, the part of the ability attempting to do something to the object will fail to do anything. The ability could be unable to find the object because the object never entered the specified zone, because it left the zone before the ability resolved, or because it is in a zone that is hidden from a player, such as a library or an opponent’s hand. (This rule applies even if the object leaves the zone and returns again before the ability resolves.) The most common zone-change triggers are enters-the-battlefield triggers and leaves-the-battlefield triggers.
Enters the Battlefield
Enters-the-battlefield abilities trigger when a permanent enters the battlefield. These are written, “When [this object] enters the battlefield,…” or “Whenever a [type] enters the battlefield,…” (Murderous Redcap, Soul's Attendant).
Each time an event puts one or more permanents onto the battlefield, all permanents on the battlefield (including the newcomers) are checked for any enters-the-battlefield triggers that match the event.
Continuous effects that modify characteristics of a permanent do so the moment the permanent is on the battlefield (and not before then). The permanent is never on the battlefield with its unmodified characteristics. However, continuous effects don’t apply before the permanent is on the battlefield.
Leaves the Battlefield
Leaves-the-battlefield abilities trigger when a permanent moves from the battlefield to another zone, or when a phased-in permanent leaves the game because its owner leaves the game. These are written as, but aren’t limited to, “When [this object] leaves the battlefield,...” or “Whenever [something] is put into a graveyard from the battlefield,...” (Kalastria Highborn). An ability that attempts to do something to the card that left the battlefield checks for it only in the first zone that it went to. An ability that triggers when an object is put into a certain zone “from anywhere” is never treated as a leaves-the-battlefield ability, even if that object is put into that zone from the battlefield (Emrakul, the Aeons Torn).
Trigger Event Verification
Normally, objects that exist immediately after an event are checked to see if the event matched any trigger conditions. Continuous effects that exist at that time are used to determine what the trigger conditions are and what the objects involved in the event look like.
However, some triggered abilities must be treated specially. They will trigger based on their existence, and the appearance of objects, prior to the event rather than afterward. The game has to “look back in time” to determine if these abilities trigger.
- Leaves-the-battlefield abilities (Kalastria Highborn).
- Abilities that trigger when a card leaves a graveyard (Erebos's Titan).
- Abilities that trigger when a permanent phases out (Ertai's Familiar).
- Abilities that trigger when an object that all players can see is put into a hand or library (Stormfront Riders).
- Abilities that trigger specifically when an object becomes unattached (Grafted Wargear).
- Abilities that trigger when a player loses control of an object (Duplicity).
- Abilities that trigger when a player planeswalks away from a plane.
Triggered Abilities of Auras
Some Auras have triggered abilities that trigger on the enchanted permanent leaving the battlefield. These triggered abilities can find the new object that permanent card became in the zone it moved to; they can also find the new object the Aura card became in its owner’s graveyard after state-based actions have been checked.
- Examples: Gift of Immortality and Fool's Demise
Replacement Effects, not Triggered Abilities
Some permanents have text that reads “[This permanent] enters the battlefield with...” (Chimeric Mass), “As [this permanent] enters the battlefield...” (Meddling Mage), “[This permanent] enters the battlefield as...” (Clone), or “[This permanent] enters the battlefield tapped” (Boros Guildgate). Such text is a static ability, not a triggered ability, whose effect occurs as part of the event that puts the permanent onto the battlefield.
Delayed Triggered Abilities
An effect may create a delayed triggered ability that can do something at a later time. A delayed triggered ability will contain “when”, “whenever”, or “at”, although that word won’t usually begin the ability.
Delayed triggered abilities come from spells or other abilities that create them on resolution, or are created as the result of a replacement effect being applied. That means a delayed triggered ability won’t trigger until it has actually been created, even if its trigger event occurred just beforehand. Other events that happen earlier may make the trigger event impossible.
- Examples: Sneak Attack, Howl of the Horde.
A delayed triggered ability will trigger only once, the next time its trigger event occurs, unless it has a stated duration, such as “this turn”.
A delayed triggered ability that refers to a particular object still affects it even if the object's characteristics change. However, if that object is no longer in the zone it’s expected to be in at the time the delayed triggered ability resolves, the ability won’t affect it.
Source of a Delayed Triggered Ability
If a spell creates a delayed triggered ability, the source of that delayed triggered ability is that spell. The controller of that delayed triggered ability is the player who controlled that spell as it resolved.
If an activated or triggered ability creates a delayed triggered ability, the source of that delayed triggered ability is the same as the source of that other ability. The controller of that delayed triggered ability is the player who controlled that other ability as it resolved.
If a static ability generates a replacement effect which causes a delayed triggered ability to be created, the source of that delayed triggered ability is the object with that static ability. The controller of that delayed triggered ability is the same as the controller of that object at the time the replacement effect was applied.
Reflexive Triggered Abilities
A resolving spell or ability may allow a player to take an action and create a triggered ability that triggers “When (a player) (does or doesn’t)” take that action. These reflexive triggered abilities follow the rules for delayed triggered abilities, except that they’re checked immediately after being created and trigger based on whether the trigger event occurred earlier during the resolution of the spell or ability that created them.
- Example: Sacrificing a creature to Heart-Piercer Manticore’s ability
Abilities Triggered by the Game State
Some triggered abilities trigger when a game state (such as a player controlling no permanents of a particular card type) is true, rather than triggering when an event occurs.
These abilities trigger as soon as the game state matches the condition. They’ll go onto the stack at the next available opportunity. These are called state triggers. (Note that state triggers aren’t the same as state-based actions.) A state-triggered ability doesn’t trigger again until the ability has resolved, has been countered, or has otherwise left the stack. Then, if the object with the ability is still in the same zone and the game state still matches its trigger condition, the ability will trigger again.
Some triggered abilities trigger specifically when a player loses the game. These abilities trigger when a player loses or leaves the game, regardless of the reason, unless that player leaves the game as the result of a draw.