307. States of the Turn
308. At any given time, the turn is in either a Neutral State or a Showdown State.
308.1. If a Showdown is in progress, the turn is in a Showdown State.
308.1.a. Only cards and abilities with the Action or Reaction keywords can be played or activated in
a Showdown State.
308.2. If no Showdown is in progress, the turn is in a Neutral State.
309. At any given time, the turn is in either an Open State or a Closed State.
309.1. If a Chain exists, the turn is in a Closed State.
309.1.a. Only cards and abilities with the Reaction keyword can be played or activated in a Closed
State.
309.2. If no Chain exists, the turn is in an Open State.
310. These descriptions can be combined, such that the turn is always in one of these four states:
310.1. Neutral Open: There is no Showdown in progress and no Chain exists.
310.1.a. By default, cards can be played and abilities activated only when a player has priority on their
turn in a Neutral Open state.
310.2. Neutral Closed: There is no Showdown in progress and a Chain exists.
310.3. Showdown Open: A Showdown is in progress and no Chain exists.
310.4. Showdown Closed: A Showdown is in progress and a Chain exists.
311. Priority and Focus
312. At any given time, up to one player has Priority.
312.1. Priority is the permission to take Discretionary Actions.
See rule 398.1. Discretionary Actions for more information.
312.1.a. The player with Priority can take appropriately timed Discretionary Actions.
312.1.b. If no player has Priority, no player can take Discretionary Actions.
312.1.b.1. Players can always take and make choices for Limited Actions when instructed,
regardless of Priority.
312.2. A player receives Priority at the following times:
312.2.a. When the turn is in a Neutral Open State during their Action Phase.
312.2.b. When the turn is in a Showdown State and they gain Focus.
312.2.c. When the turn is in a Closed State and they control the next item on the Chain.
312.2.d. When the turn is in a Closed State, they are the next Player in Turn Order, and the player
with Priority passes.
313. At any given time, up to one player has Focus.
313.1. Focus is the permission to take appropriately timed Discretionary Actions when the turn is in a
Showdown Open State.
See rule 307. States of the Turn for more information.
313.1.a. The player with Focus must obey any additional restrictions on which Discretionary Actions
may be performed.
Example: A player with Focus may not play spells or activate abilities that don't
have the Action or Reaction keywords.
313.2. A player who gains Focus also gains Priority.
313.3. A player who passes Priority retains Focus.
313.4. If the turn is in a Neutral State, no player has Focus.
314. Phases of the Turn
315. Start of Turn
315.1. Awaken Phase
315.1.a. The Turn Player readies all Game Objects they control that are able to be readied.
See rule 402. Ready for more information.
315.2. Beginning Phase
315.2.a. Beginning Step
315.2.a.1. At the start of Beginning Phase game effects take place.
315.2.b. Scoring Step
315.2.b.1. Holding occurs at this time.
See rule 441. Scoring for more information.
315.2.b.2. Reminder: In Modes of Play with Teams, Battlefields held by a Teammate of the
Turn Player during this phase are disqualified from being scored this turn by the
Turn Player.
315.2.c. Specific game effects or abilities will reference this timing and phase as necessary.
315.3. Channel Phase
315.3.a. The Turn Player gains their additional runes for the turn.
315.3.b. The Turn Player channels 2 runes from their Rune Deck.
See rule 417. Channel for more information.
315.3.b.1. If there are fewer than 2 runes in the Rune Deck, they channel as many as possible.
315.3.c. Perform any actions as instructed by game objects during this time.
315.4. Draw Phase
315.4.a. The Turn Player gains their additional card for the turn.
315.4.b. The Turn Player draws 1.
315.4.b.1. If there are no cards remaining in their Main Deck to draw, the Turn Player has
been Burned Out.
See rule 418. Burn Out for more information.
315.4.b.2. After completing the Burn Out the Turn Player still Draws 1.
315.4.c. Perform any actions as instructed by game objects during this time.
315.4.d. As the Draw Phase ends, each player's Rune Pool empties.
See rule 158. Rune Pools for more information
Source: https://riftbound.gg/core-rules/
324. Chains and Showdowns
325. Players can act during the following Windows of Opportunity that occur during the course of regular play:
325.1. During a Chain
325.2. During a Showdown
326. Chains
327. The Chain is a Non-Board Zone that temporarily exists whenever a card is played or an ability is activated.
327.1. Cards are placed here as part of the process of being played.
327.2. Abilities are queued here as part of the process of resolving.
See rule 357. Abilities for more information.
328. Cards and abilities added to the chain are added as Pending Chain Items that become Finalized Chain Items.
328.1. Pending Items are on the Chain.
328.2. Chain Items are Pending until the “Check Legality” step of playing a card.
See rule 346. Playing Cards for more information.
328.3. When a Pending Chain Item is no longer Pending it is finalized and becomes a Finalized Chain Item.
329. The Chain exists as long as a Chain Item is on it.
329.1. Only one Chain can exist at a time.
329.2. If a card would begin to be played while a Chain already exists, it is placed on the existing Chain.
330. The State of the Turn is partially determined by whether or not the Chain currently exists.
330.1. The turn is said to be in a Closed State if a Chain exists.
330.1.a. Cards of all Categories, by default, cannot be played during a Closed State.
330.1.b. Card abilities, by default, cannot be played during a Closed State.
330.2. The turn is said to be in an Open State if no Chain exists.
331. Steps of Resolving Chain Items
332. Whenever a card or token is played or an ability is activated or triggered, a Chain is created.
332.1. The player that created the chain becomes the first Active Player.
332.2. The Active Player is a designator similar to, but distinct from, Turn Player.
332.3. Similar to the Turn Player, this designation will pass between players over the course of play.
333. Step 1: Finalize
333.1. If one or more Items are Pending, their controllers must complete the steps of Playing those
Pending Items until they are Finalized Items or leave the Chain.
333.1.a. This process does not pass Priority.
333.1.b. Each Item is Finalized in the order it was appended to the Chain.
333.1.c. Abilities that Add resources, Units, and Gear resolve immediately when Finalized and do not
progress to Step 2: Execute.
See rule 346. Playing Cards for more information.
333.1.c.1. If the Chain is empty, play proceeds in an Open State.
333.1.c.2. If the Chain is not empty and there are one or more Pending Items, repeat Step 1.
333.1.c.3. If the Chain is not empty and there are no Pending Items, the controller of the
newest item on the chain gains Priority and becomes the Active Player. Proceed
to Step 2: Execute.
334. Step 2: Execute
334.1. The Active Player may do any the following:
334.1.a. Play a Card that is legally timed.
334.1.a.1. Cards, by default, cannot be played during a Closed State.
334.1.a.2. A Legally Timed Card would be a Card with Reaction.
334.1.a.3. Other exceptions may be created during regular play.
334.1.a.4. The card will be added to the chain as a Pending Item, following the steps of
playing a card.
334.1.a.5. This can be an additional card to the item that Started the Chain in the case of the
first Active Player after creating the Chain.
334.1.a.6. Whether a Card is legally timed is evaluated during the “Check Legality” step of
Playing a Card.
See rule 346. Playing Cards for more information.
334.1.a.7. Playing a card will create one or more Pending Items. Return to Step 1: Finalize.
334.1.b. Activate Abilities of Game Objects that are legally timed.
See rule 386. Playing or Activating Abilities for more information.
334.1.b.1. All rules for legally timed cards apply to legally timed abilities.
334.1.b.2. Activating abilities will create one or more Pending Items. Return to Step 1: Finalize.
334.1.c. Pass Priority
334.1.c.1. The Active Player passes Priority to the next Player in Turn Order. Proceed to Step
3: Pass.
335. Step 3: Pass
335.1. If all players have passed Priority without adding any items to the Chain, proceed to Step 4: Resolve.
335.2. Otherwise, the Active Player passes Priority to the next Player in Turn Order. Return to Step 3:
Execute.
336. Step 4: Resolve
336.1. The newest item on the Chain resolves. Execute its game effects in their entirety.
See rule 346. Playing Cards for more information on resolving spells.
See rule 386. Playing or Activating Abilities for more information on resolving abilities.
336.2. If the Chain is empty, play proceeds in an Open State.
336.3. If the Chain is not empty and there are one or more Pending Items, return to Step 1: Finalize.
336.4. If the Chain is not empty and there are no Pending Items, the controller of the newest item on the
chain gains Priority and becomes the Active Player. Return to Step 2: Execute.
350. The Process of Play
351. 1. Remove the card from the zone you are playing it from and put it onto the Chain.
351.1. This Closes the State.
See rule 307. States of the Turn for more information.
351.2. This item becomes Pending.
351.3. If another Card Effect or ability is currently resolving, continue resolving it before proceeding with any
further steps of this process.
352. 2. Make necessary choices.
352.1. If the card is a spell, or has an effect that specifies a choice "As I am played," those choices are made
now.
352.2. For Units, choose a valid Location where that Unit will be placed upon being Played.
352.3. For Spells and Abilities that Move one or more Units, choose a valid Location as the Move
Destination for each Move that will be performed.
352.4. If a card requires you to specifically choose one or more Game Objects, that choice is made now.
352.4.a. This does not include cards that affect one or more Game Objects based on criteria.
Example: "Stun a unit at a battlefield" is a Choice.
Example: "Kill all gear" is not a Choice.
352.4.b. This does not include making choices for Triggered Abilities of permanents, even if those
abilities trigger when the permanent is played.
Example: A unit with a triggered ability that says "When I'm played, kill a unit" does
not require you to choose a target as it's played. The target will be chosen when the
ability triggers.
See rule 375. Triggered Abilities for more information.
352.5. Targeting
352.6. When a card Chooses one or more specific Game Objects to affect, it is Targeted.
352.7. In order to put a spell or ability on the chain, valid choices must be made for all targets.
352.8. A target is a valid choice if it meets all of the following requirements:
352.8.a. It is a permanent or rune on the board, a spell or ability on the chain, a player or zone, or
specified explicitly or implicitly as being in some other zone.
e.g., “Kill a unit” targets a unit on the board.
e.g., “Recycle a unit from your trash” targets a unit card in your trash.
352.8.a.1. “Unit,” “gear,” and “rune” refer to objects on the Board unless specified otherwise.
352.8.a.2. “Spell” and “ability” refer to objects on the Chain unless specified otherwise.
352.8.a.3. “Facedown card” refers to a card in a Facedown Zone unless specified otherwise.
352.8.a.4. “Legend” refers to a legend in the Legend Zone.
352.8.a.5. “Chosen Champion” and “unit in the Champion Zone” refer to a unit in the
Champion Zone unless specified otherwise.
352.8.b. It meets all targeting restrictions.
e.g., A unit is a valid target for a spell that refers to a “unit at a battlefield,” “enemy
unit,” “unit you control,” or “unit with Might 4 or greater” only if it meets the
appropriate criteria.
352.8.c. It is not the spell or ability itself.
e.g., A spell that says “Counter a spell” cannot target itself.
e.g., An ability of a permanent can target that permanent, because abilities and
their sources are separate objects.
352.9. If a spell or ability requires one or more players to choose objects, players, or zones that are not
targets, those choices are made on resolution.
352.9.a. Passive abilities never have targets.
352.9.b. Replacement effects never have targets.
352.9.c. Units and gear never have targets, although their abilities may.
352.10. A game object, player, or zone mentioned in the text of a spell, activated ability, or triggered ability is a
target UNLESS any of the following are true:
352.10.a. It is in a zone whose information status is not Public.
e.g., “Ready a legend” targets a legend, because the Legend Zone is Public.
e.g., “Return a unit from your trash to your hand” targets a unit card in your trash,
because your trash is Public.
e.g., “You may play a unit from your hand, ignoring its costs” does not target a unit
card in your hand, because your hand is not a public zone.
352.10.a.1. Public zones are Battlefield Zones, Bases, Trashes, Legend Zones, Champion Zones,
and Facedown Zones.
352.10.b. It is included only as part of a targeting restriction for another choice.
e.g., “Kill a unit at a battlefield” targets a unit, but not a battlefield, because the
units are targets and “at a battlefield” is a restriction.
e.g., “Kill all units at a battlefield” targets a battlefield, but not any units.
e.g., “Move a unit to a battlefield” targets both a unit and a battlefield.
352.10.c. It is included only as part of a cost, trigger condition, or replacement effect.
e.g., “As an additional cost to play me, kill a friendly unit” doesn’t target anything.
e.g., “When a friendly unit dies, kill a gear” targets a gear, but not a friendly unit.
e.g., “When you play me, the next time a friendly unit would die this turn, return it
to your hand instead” doesn’t target anything. The replacement effect applies
when any friendly unit dies.
e.g., “Choose a friendly unit. The next time it would die this turn, return it to your
hand instead” targets a friendly unit, because “choose a friendly unit” is not part of
the replacement effect.
352.10.c.1. This includes costs within instructions, identified by phrases like “[do X] to [do Y].”
The cost within that instruction is “[do X].”
e.g., “When I hold, you may kill another friendly unit here to draw 1” does
not target anything.
e.g., “When you play me, you may spend a buff to move a friendly unit”
targets the friendly unit, but not the buff.
352.10.d. It is programmatically selected based on its characteristics rather than chosen by the spell or
ability’s controller.
e.g., “Kill all units at a battlefield” targets a battlefield, but does not target any
units.
e.g., “Kill all units at battlefields” doesn’t target anything.
e.g., “Destroy a unit. Its controller draws 2 cards” targets the unit, but not its
controller.
e.g., “Ready your legend” doesn’t target anything, because you can only have one
legend.
e.g., “Ready a friendly legend” targets a legend, because in a 2v2 game there are
two friendly legends.
e.g., “Recycle all cards in your trash” doesn’t target anything, because it affects all
cards and you only have one trash.
352.10.d.1. This exception applies solely to objects for which no choice is ever possible.
352.10.d.2. This exception does not apply to objects that are the only valid choice at the
moment a spell or ability is placed on the chain, but which would require a choice
under other circumstances.
e.g., “Kill a unit at a battlefield” always targets a unit, even if that unit is
the only unit currently at a battlefield.
352.10.e. It is part of a set of objects chosen in whole or in part by other players.
e.g., “Each player kills a unit they control” does not target. Each player, including
the one who played the spell, chooses a unit to kill as the spell or ability resolves.
352.10.f. It is identified in an instruction that a player “must” complete.
e.g., “You must recycle one of your runes” doesn’t target anything. You choose from
among your runes as the spell or ability resolves.
e.g., “Recycle a rune you control” targets a rune. You choose a rune you control as
you put the spell or ability on the chain.
352.11. Some cards identify a group of Targets with Targeting Requirements that must be met by the
group as a whole.
352.11.a. As they’re finalized on the chain, such cards can choose any group of valid targets that
collectively fulfill the targeting restriction.
352.11.b. If the group of targets no longer collectively fulfill the targeting restriction as the spell or
ability resolves, that spell or ability’s controller can choose a subset of the original targets
that fulfills the targeting requirement for the spell or ability to affect.
Example: A player plays Fox-Fire, a spell that says in part “Kill any number of units at
a battlefield with total Might 4 or less.” That player chooses four 1 [M] Recruit tokens
at a single battlefield. As a Reaction, another player gives two of those Recruits +1
[M], so the Recruits’ Mights are 1, 1, 2, and 2. Then Fox-Fire resolves. The Recruits no
longer have total Might 4 or less, so Fox-Fire’s controller must choose a legal subset
of the original targets to affect. They could choose to kill the two 2 [M] Recruits, or
the two 1 [M] Recruits plus one 2 [M] Recruit. The units they choose are Fox-Fire’s
remaining legal targets. They can’t choose to affect units at the same battlefield
that weren’t initially chosen as targets, and they can’t affect any units that are no
longer at the chosen battlefield.
352.12. If a card specifies that a player may choose some number of Game Objects to be affected by a card,
then all choices are considered targeted and chosen independently.
352.13. If a card specifies that a player chooses “any number” or “up to” some number of Game Objects to be
affected, they may choose any number of available targets, including zero. If they choose zero, the
spell or ability can be played without any targets.
352.14. Splitting
352.14.a. If a card specifies that an amount of damage may be split among some number of Units,
then each Unit chosen is Targeted.
352.14.b. The Targets are chosen when the spell or ability is finalized on the chain.
352.14.c. A number of Targets can only be chosen up to, and not exceeding, the initial amount of
damage available when the spell is played. Example: A player playing a spell that instructs
them to "Split 5 damage" may only choose up to 5 units, but may choose fewer.
352.14.d. Each Target is valid, and contributes to Chosen triggers individually.
352.14.e. The choice of how much damage is divided across the split is not decided until the
resolution of the spell or ability.
352.14.f. Each Target must receive a valid amount of damage.
352.14.g. Valid damage is a positive integer amount, greater than or equal to 1 damage.
352.14.h. If, at resolution of the spell or effect, there are more Targets than available damage to divide,
then the player who controls the effect dealing damage determines which Targets cease
being Targets.
352.14.i. Any costs that were paid, or effects that were triggered as a result of those Game Objects
being chosen as Targets remain in effect, paid, or otherwise triggered.
352.15. These choices cannot be changed after this step.
352.16. A player may not make choices during this step that will deterministically result in illegal choices or
actions later in this process unless they have no choice.
Example: A player plays Cruel Patron, which says "As an additional cost to play me, kill a
friendly unit." They control exactly one unit, which is at a battlefield. They can't choose to play
Cruel Patron to that battlefield, because by the time they have finished paying costs, they
will no longer control that battlefield.
353. 3. Determine Total Cost.
353.1. If an ability or instruction allows you to "ignore" one or more of a card's costs, set the appropriate Base
Cost(s) of the card to zero.
353.1.a. If a card allows a player to play a card "ignoring its cost," its base Energy cost and base
Power cost are set to zero.
353.1.b. If a card instructs a player to play a card "ignoring its Energy cost" or "ignoring its Power
cost," only the appropriate cost is set to zero, and the remaining cost still applies.
353.1.c. Further additional costs and/or cost increases applied in subsequent steps may raise the
card's Total Cost above zero.
Example: Legion Rearguard is a Fury unit that costs 2 Energy and 0 Power and has
Accelerate. A player plays Legion Rearguard and is instructed to ignore its costs, but
chooses to pay the Accelerate cost. They ignore Legion Rearguard's Base Cost of 2
Energy, but the optional additional cost of 1 Energy and 1 Fury Power is added to its
Total Cost and must be paid.
353.2. Apply additional costs in any order.
353.2.a. Mandatory Additional Costs
353.2.a.1. Some Additional Costs specified by Passive Abilities on the card being played or
another card are Mandatory, and must be paid to complete playing the card. They
use the phrase "as an additional cost" and don't include the word "may."
Example: A unit has the passive ability "As an additional cost to play me,
kill a friendly unit." To play that unit, a player must kill a friendly unit.
See rule 360. Passive Abilities for more information.
353.2.a.2. The cost imposed by the Deflect keyword is a Mandatory Additional Cost.
See rule 725. Deflect for more information.
353.2.b. Optional Additional Costs
353.2.b.1. Some Optional Costs specified by Passive Abilities on the card being played or
another card are Non-Mandatory, and must be paid only if the player made the
choice to pay them in rule 352. They use the phrase "as an additional cost" and the
word "may."
Example: A unit has the ability "As you play me, you may discard 1 as an
additional cost. If you do, reduce my cost by [2]." While playing the unit, its
controller declares their intention to pay the additional cost in rule 352,
applies that additional cost in rule 353.2, applies the discount granted by
paying that cost in rule 353.4, and discards a card to pay that additional
cost in rule 354.2.
See rule 360. Passive Abilities for more information.
353.3. Apply cost increases.
353.4. Apply discounts in any order.
353.4.a. Discounts may be applied by the card being played or by any other card or effect.
353.4.b. Discounts may say that cards "cost [amount] less" or that one or more of their costs are
"reduced by [amount]."
353.4.c. If a discount applies a minimum cost, that minimum applies only to that discount.
Example: Eager Apprentice says "While I'm at a battlefield, the Energy costs for
spells you play is reduced by [1], to a minimum of [1]." A player who controls Eager
Apprentice and a unit with 7 Might plays Sky Splitter, a spell that costs 8 Energy
and says "This spell's Energy cost is reduced by the highest Might among units you
control." That player can choose to apply Eager Apprentice's discount first, reducing
Sky Splitter's Energy cost to 7, then apply Sky Splitter's discount, reducing its Energy
cost to 0. If they applied these discounts in the other order, Sky Splitter's Energy
cost would be 1.
353.4.d. Discounts can reduce additional costs, including to 0.
353.4.d.1. An optional additional cost was "paid" if the player made the decision in rule 352 to
pay it. It doesn't matter how much the player actually paid.
Example: Clockwork Keeper is a unit that costs 2 Energy and 0 Power and
says "As you play me, you may pay [C] as an additional cost. If you do, draw
" A player controls a card that says "Units you play cost [A] less." That player
plays Clockwork Keeper and chooses to pay the optional additional cost of
[C]. They will draw a card, even though the optional additional cost was
reduced to 0.
353.5. Energy and Power costs can't be reduced below 0.
353.6. Costs may be Energy costs, Power costs, or non-standard costs. Example: A card reads "As an
additional cost to play me, kill a friendly unit." Killing a friendly unit is an additional cost to play that
card.
354. 4. Pay the card's costs.
354.1. In total, pay the combined Energy cost (if any) and Power cost (if any).
354.1.a. During this step, the spell's controller can use activated abilities with the Reaction tag that
Add resources to add Energy and Power to pay the spell's costs.
See rule 158. Rune Pools and rule 416. Add for more information.
354.2. In addition, pay any non-standard Cost summed in rule 353.2 in any order.
354.2.a. Costs that are replaced with other events by replacement effects are still considered paid.
Example: A player plays Cruel Patron, which says "As an additional cost to play me,
kill a friendly unit." They also control Zhonya’s Hourglass, which says “If a friendly
unit would die, kill this instead. Heal that unit, exhaust it, and recall it.” They choose
to kill a friendly unit during rule 353.2, but as they pay the cost in rule 354.2,
Zhonya’s Hourglass replaces that unit’s death. The cost is considered paid, and the
player can continue playing Cruel Patron.
354.3. A player may not pay costs during this step that will deterministically result in illegal choices or
actions later in this process unless they have no choice.
Example: A player plays Cruel Patron, which says "As an additional cost to play me, kill a
friendly unit." They control multiple units, one of which is alone at a battlefield. During rule
352.2., they chose to play Cruel Patron to that battlefield. While paying costs, they can't
choose to kill the unit at that battlefield, because then they will no longer control that
battlefield and Cruel Patron cannot legally be played there. If they controlled that battlefield
with multiple units, any of those units would be a legal choice, because they would still
control the battlefield after killing one.
355. 5. Check legality.
355.1. Check that all chosen targets are legal.
355.2. Ensure that the outcome of the effect of this card being played would not create an illegal state.
Example: Check that a spell's execution does not create a state where a Battlefield has Units
controlled by 3 different players.
355.3. If the card, if continued to be played, would create an illegal state, or if a choice or action at this state
is illegal, the actions taken in this process are undone and the action is cancelled.
356. 6. Finalize this card and proceed with the card's category of Play.
356.1. This card is no longer Pending.
356.2. A Permanent leaves the Chain and becomes a Game Object.
356.2.a. Any passive abilities become active.
356.2.b. Execute all rules text on the card, from top to bottom.
356.2.c. If it is a Unit, it enters the Board exhausted at the Location that was chosen.
356.2.d. If it is a Gear, it enters the Board Ready at the player's Base.
356.3. A Spell lingers on the Chain.
356.3.a. This card becomes a Finalized Chain Item.
356.3.b. If there are other Pending Items on the Chain, then the controller of those Pending Items
completes Steps 2 through 5 of Playing Cards for those items before continuing.
See rule 326. Chains for more information.
356.3.c. Other players have an opportunity to play Reactions before the resolution of spells.
See rule 326. Chains for more information.
356.3.d. Otherwise, execute the game effect of the spell, from top to bottom of the rules text of the
card and then place the card in the Trash of the owning player.
356.3.e. Handling illegal and impossible instructions
356.3.e.1. The spell resolves even if some or all of its targets are illegal.
356.3.e.2. A target is illegal as the spell resolves if it no longer meets the targeting
requirements of the spell, or if it has changed Zones to or from a Non-Board Zone.
356.3.e.3. If a target ceases to meet the targeting requirements while the spell is on the chain,
then meets them again, it's a legal target.
Example: A spell targets "a unit at a battlefield." A player reacts with a spell
that moves the unit to base, then another player reacts with a spell that
moves it back to that battlefield, then the original spell resolves. The unit is
a legal target.
356.3.e.4. If a target changes Zones to or from a Non-Board Zone and then returns to its
original zone, it is no longer a legal target, because it's not treated as the same
object.
Examples:
An enemy unit at a battlefield is no longer a legal target if it is no longer an
enemy, no longer a unit, or no longer at a battlefield.
A unit with 3 or less Might is no longer a legal target if it is no longer a unit
or if its Might is greater than 3.
Something that's exhausted is no longer a legal target if it is no longer
exhausted. (It can't stop being "something.")
A spell that's played from hidden has the additional targeting requirement
"here." A target for such a spell ceases to be a legal target if it moves from
the battlefield where that spell was played, even if the spell has no location
targeting requirement otherwise.
356.3.e.5. If any of the spell's targets are no longer legal, those targets are unaffected by the
spell as it resolves.
Example: A player plays Void Seeker, a spell that says "Deal 4 to a unit at a
battlefield. Draw 1." The unit's controller uses a Reaction to move the unit
to their base. Since the unit is no longer a legal target, it is not dealt any
damage. Void Seeker's controller still draws 1.
356.3.e.6. Instructions that can't be followed, either because of illegal targets or other
circumstances, are ignored.
356.3.e.7. If all of an instruction's Targets become Invalid or Unavailable by the time the
spell is finished being played, that instruction will not execute.
356.3.e.8. If an instruction has more than one Target and fewer than all of the Targets
become Invalid or Unavailable by the time the spell is finished being played, the
instruction will execute, with only the Targets available and valid being operated
on.
356.3.e.9. The process for a card's choice becoming Invalid or Unavailable is referred to as
mistargeting.
Example: A spell has the instruction "Deal 2 to a unit at a battlefield."
Before that instruction can execute, the chosen unit is moved to its base.
The instruction will not be executed, because it specifies that the unit it
chooses must be at a Battlefield, and by the time it attempted to execute,
the unit was no longer valid as a choice.
356.3.e.10. It is possible for none of a spell's instructions to be executed as it resolves, due to all
of them requiring targets to act on and all of those targets becoming Invalid or
Unavailable. In this case, the spell has no effect but is still considered played.
Example: A player plays a spell that reads "Deal 2 to a unit at a battlefield"
with no other instructions, and chooses an enemy unit at a battlefield.
They also control a unit with the ability "When you play a spell, give me +1
[M] this turn." Before the spell resolves, the chosen unit is moved to its
base. The spell resolves and its only instruction cannot be executed, but
the unit's ability still triggers as the spell resolves and gives it +1 [M].
356.3.e.11. Instructions that can be partially followed are followed as much as possible and
ignored otherwise.
Example: A player plays a spell that says "Discard 2, then draw 2" If their
hand is empty, the instruction to discard 2 will be ignored. They'll still draw
2. If they had 1 card in hand, they would discard it and draw 2.
356.3.e.12. If the spell checks information about a target that is no longer legal or a card or
permanent whose location, zone, or status has changed such that that information
is no longer available, that check returns "null" and all calculations based on it are
ignored.
Examples:
A unit that is no longer on the board is treated as having null Might, null
cost, etc.
A unit that is no longer on the board has no location, is neither exhausted
nor readied, etc.
Baited Hook says "[1][C], [E]: Kill a friendly unit. Look at the top 5 cards of
your Main Deck. You may banish a unit from among them that has Might
up to 1 more than the killed unit and play it, ignoring its cost. Then recycle
the rest." While Baited Hook’s ability is on the chain, an opponent reacts
with a spell that returns the friendly unit to its owner's hand. Because the
friendly unit is no longer a legal target, it can't be killed and its Might is
treated as null. Baited Hook’s controller reveals the top 5 cards of their
Main Deck, but can’t choose any unit from among them.
356.3.e.13. A spell or ability that moves something to a different zone as a cost or effect can
"look back" at its characteristics before it changes zones.