408.2g Game actions don’t use the stack. The game actions are phasing in and out during the untap step (see rule 302.1), untapping during the untap step (see rule 302.2), drawing a card during the draw step (see rule 304.1), declaring attackers at the start of the declare attackers step (see rule 308.1), declaring blockers at the start of the declare blockers step (see rule 309.1), cleanup (see rule 314), and mana burn as each phase ends (see rule 300.3).
408.2h The controller of a face-down permanent may turn it face up. This is a special action. (See rule 504, “Face-Down Spells and Permanents.”) A player can turn a face-down permanent face up only when he or she has priority. That player gets priority after this special action.
408.2i Some effects allow a player to take an action at a later time, usually to end a continuous effect or to stop a delayed triggered ability. This is a special action. A player can end a continuous effect or stop a delayed triggered ability only if the effect or ability allows it and only when he or she has priority. The player who took the action gets priority after this special action.
408.2j Some effects from static abilities allow a player to take an action to ignore the effect from that ability for a duration. This is a special action. A player can take an action to ignore an effect only when he or she has priority. The player who took the action gets priority after this special action.
408.2k A player who has a card with suspend in his or her hand may remove that card from the game. This is a special action. (See rule 502.59, “Suspend.”) A player can remove a card with suspend in his or her hand from the game only when he or she has priority. That player gets priority after this special action.
409.1. Playing a spell or activated ability follows the steps listed below, in order. If, at any point during the playing of a spell or ability, a player is unable to comply with any of the steps listed below, the spell was played illegally; the game returns to the moment before that spell or ability was played (see rule 422, “Handling Illegal Actions”). Announcements and payments can’t be altered after they’ve been made.
409.1a The player announces that he or she is playing the spell or activated ability. It moves from the zone it’s in to the stack and remains there until it’s countered or resolves. In the case of spells, the physical card goes onto the stack. In the case of activated abilities, the ability goes onto the stack without any card associated with it. If the ability is being played from a hidden zone, the card with that ability is revealed. Each spell has all the characteristics of the card associated with it. Each activated ability on the stack has the text of the ability that created it, and no other characteristics. The controller of a spell is the player who played the spell. The controller of an activated ability is the player who played the ability.
409.1b If the spell or ability is modal (uses the phrase “Choose one -” or “[specified player] chooses one -”), the player announces the mode choice. If the player wishes to splice any cards onto the spell, he or she reveals those cards in his or her hand. If the spell or ability has a variable mana cost (indicated by {X}) or some other variable cost, the player announces the value of that variable at this time. If the spell or ability has alternative, additional, or other special costs (such as buyback, kicker, or convoke costs), the player announces his or her intentions to pay any or all of those costs (see rule 409.1f). You can’t apply two alternative methods of playing or two alternative costs to a single spell or ability. Previously made choices (such as choosing to play a spell with flashback from his or her graveyard or choosing to play a creature with morph face down) may restrict the player’s options when making these choices.
409.1c If the spell or ability requires any targets, the player first announces how many targets he or she will choose (if the spell or ability has a variable number of targets), then announces the targets themselves. A player can’t play a spell or ability unless he or she chooses the required number of legal targets. The same target can’t be chosen multiple times for any one instance of the word “target” on the spell or ability. If the spell or ability uses the word “target” in multiple places, the same object, player, or zone can be chosen once for each instance of the word “target” (as long as it fits the targeting criteria).
Example: If an ability reads “Tap two target creatures,” then the same target can’t be chosen twice; the ability requires two different legal targets. An ability that reads “Destroy target artifact and target land,” however, can target the same artifact land twice because it uses the word “target” in multiple places.
409.1d If the spell or ability targets one or more targets only if an alternative, additional, or special cost (such as a buyback or kicker cost) is paid for it, or if a particular mode is chosen for it, its controller chooses those targets only if he or she announced the intention to pay that cost or chose that mode. Otherwise, the spell or ability is played as though it did not have those targets.
409.1e If the spell or ability affects several targets in different ways, the player announces how it will affect each target. If the spell or ability requires the player to divide or distribute an effect (such as damage or counters) among one or more targets, or any number of untargeted objects or players, the player announces the division. Each of these targets, objects, or players must receive at least one of whatever is being divided.
409.1f The player determines the total cost of the spell or ability. Usually this is just the mana cost (for spells) or activation cost (for abilities). Some cards list additional or alternative costs in their text, and some effects may increase or reduce the cost to pay. Costs may include paying mana, tapping permanents, sacrificing permanents, discarding cards, and so on. The total cost is the mana cost, activation cost, or alternative cost, plus all cost increases and minus all cost reductions. Once the total cost is determined, it becomes “locked in.” If effects would change the total cost after this time, they have no effect.
409.1g If the total cost includes a mana payment, the player then has a chance to play mana abilities (see rule 411, “Playing Mana Abilities”). Mana abilities must be played before costs are paid.
409.1h The player pays the total cost in any order. Partial payments are not allowed.
Example: You play Death Bomb, which costs {3}{B} and has an additional cost of sacrificing a creature. You sacrifice Thunderscape Familiar, whose effect makes your black spells cost {1} less to play. Because a spell’s total cost is “locked in” before payments are actually made, you pay {2}{B}, not {3}{B}, even though you’re sacrificing the Familiar.