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0020: Stack removal, rule causes, and other review gaps ​

Status: Accepted

Context ​

The review found events with a known cause the format could not name, so writers were left with by ?: attackers becoming tapped, Saga lore counters, triggered abilities removed from the stack without resolving. It also found choices that belong to no spell or ability, "look at" effects, and prevented damage, none of which had an encoding.

Decision ​

  1. New rule causes: no-choice, intervening-if, declare-attackers, lore, replacement-order, plus duration, delayed-trigger, and day-night (decision 0026).
  2. A triggered ability with no legal choice, or no mode, is written cease by rule:no-choice straight after its new line. One whose intervening "if" is false is written resolve, then cease by rule:intervening-if.
  3. Declaring an attacker is followed by tap by rule:declare-attackers, except for creatures with vigilance.
  4. Choices that belong to no spell or ability (the legend rule, the order of replacement effects) are player statements, PLAYER choose CHOICE, with a rule cause.
  5. OBJREF look PLAYER records a player looking at a card.
  6. Prevented damage: partly prevented damage is written with the amount dealt; completely prevented damage with the amount that would have been dealt and prevented. Both add replacement ID naming the prevention effect's source.
  7. rule:resolve also covers an Aura becoming attached as it resolves.

Rules basis ​

Checked against the Comprehensive Rules effective 2026-09-25.

  • 603.3d: "if a choice is required when the triggered ability goes on the stack but no legal choices can be made for it ... the ability is simply removed from the stack." 700.2b: "If no mode is chosen, the ability is removed from the stack."
  • 608.2a: "If a triggered ability has an intervening 'if' clause, it checks whether the clause's condition is true. If it isn't, the ability is removed from the stack and does nothing."
  • 508.1f: "The active player taps the chosen creatures. Tapping a creature when it's declared as an attacker isn't a cost; attacking simply causes creatures to become tapped." 702.20b: "Attacking doesn't cause creatures with vigilance to tap."
  • 703.4f: "Immediately after a player's precombat main phase begins, that player puts a lore counter on each Saga enchantment they control".
  • 704.5j: under the legend rule, "that player chooses one of them, and the rest are put into their owners' graveyards." 616.1: the affected player "chooses one to apply".
  • 701.20e: "Looking at a card follows the same rules as revealing a card, except that the card is shown only to the specified player."
  • 615.1: prevention effects "watch for a damage event that would happen and completely or partially prevent the damage". 615.6: "If damage that would be dealt is prevented, it never happens."
  • 608.3c: an Aura spell "is put onto the battlefield under the control of the spell's controller attached to the player or object it was targeting."

Alternatives rejected ​

  • by ? for turn-based actions. Rejected: ? means unknown, and these causes are known.
  • attack implying a tap. Rejected: a parser would have to know about vigilance and every other exception. An explicit tap line is checkable.
  • No line for completely prevented damage. Rejected: the attack would appear to have dealt nothing for no reason, against design principle 4.

Consequences ​

  • See examples/more-situations.md and examples/lasting-effects.mtgr.