Get 2 mana from 2 flagstones

[RoddyVR]

An opponent on MWS just tried this:
He has flagstones of trokair in play, also has a mox diamond in play.
He wants to play a second flagstones, and tap all 3 of his sources for mana (the 2 Flagstones and the mox).
Can he tap the new flagstone before the legend rule kills them? (i know he can tap the old flagstones and the mox).
I'm not sure how "fast" the legend rule is, does it use the stack? does anyone get priority before it activates and so on...

When i told him he could only use the old stone for mana, he SPLed me, so i wanted to make sure i was right in my understanding.

[hungryLIKEALION]

You were correct, the legend rule is a state-based effect action and immediately the next time a player would get priority sends both flagstones to the graveyard.

[cdr]

You need to understand state-based actions. And using terms like "how fast" or "speed" probably isn't helping you understand either.



704. State-Based Actions (http://yawgatog.com/resources/magic-rules/#R704.)


704.1. State-based actions are game actions that happen automatically whenever certain conditions (listed below) are met. State-based actions don't use the stack.


704.1a. Abilities that watch for a specified game state are triggered abilities, not state-based actions. (See rule 603, "Handling Triggered Abilities.")

704.2. State-based actions are checked throughout the game and are not controlled by any player.

704.3. Whenever a player would get priority (see rule 115, "Timing and 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. If any state-based actions are performed as a result of a check, the check is repeated; otherwise all triggered abilities that are waiting to be put on the stack are put on the stack, then the check is repeated. Once no more state-based actions have been performed as the result of a check and no triggered abilities are waiting to be put on the stack, the appropriate player gets priority. This process also occurs during the cleanup step (see rule 514), except that if no state-based actions are performed as the result of the step's first check and no triggered abilities are waiting to be put on the stack, then no player gets priority and the step ends.

704.4. Unlike triggered abilities, state-based actions pay no attention to what happens during the resolution of a spell or ability.

Example: A player controls a creature with the ability "This creature's power and toughness are each equal to the number of cards in your hand" and casts a spell whose effect is "Discard your hand, then draw seven cards." The creature will temporarily have toughness 0 in the middle of the spell's resolution but will be back up to toughness 7 when the spell finishes resolving. Thus the creature will survive when state-based actions are checked. In contrast, an ability that triggers when the player has no cards in hand goes on the stack after the spell resolves, because its trigger event happened during resolution.

704.5. The state-based actions are as follows:


704.5a. If a player has 0 or less life, he or she loses the game.

704.5b. If a player attempted to draw a card from an empty library since the last time state-based actions were checked, he or she loses the game.

704.5c. If a player has ten or more poison counters, he or she loses the game.

704.5d. If a token is phased out, or is in a zone other than the battlefield, it ceases to exist.

704.5e. If a copy of a spell is in a zone other than the stack, it ceases to exist. If a copy of a card is in any zone other than the stack or the battlefield, it ceases to exist.

704.5f. If a creature has toughness 0 or less, it's put into its owner's graveyard. Regeneration can't replace this event.

704.5g. If a creature has toughness greater than 0, and the total damage marked on it is greater than or equal to its toughness, that creature has been dealt lethal damage and is destroyed. Regeneration can replace this event.

704.5h. If a creature has been dealt damage by a source with deathtouch since the last time state-based actions were checked, that creature is destroyed. Regeneration can replace this event.

704.5i. If a planeswalker has loyalty 0, it's put into its owner's graveyard.

704.5j. If two or more planeswalkers that share a planeswalker type are on the battlefield, all are put into their owners' graveyards. This is called the "planeswalker uniqueness rule."

704.5k. If two or more legendary permanents with the same name are on the battlefield, all are put into their owners' graveyards. This is called the "legend rule." If only one of those permanents is legendary, this rule doesn't apply.

704.5m. If two or more permanents have the supertype world, all except the one that has been a permanent with the world supertype on the battlefield for the shortest amount of time are put into their owners' graveyards. In the event of a tie for the shortest amount of time, all are put into their owners' graveyards. This is called the "world rule."

704.5n. If an Aura is attached to an illegal object or player, or is not attached to an object or player, that Aura is put into its owner's graveyard.

704.5p. If an Equipment or Fortification is attached to an illegal permanent, it becomes unattached from that permanent. It remains on the battlefield.

704.5q. If a creature is attached to an object or player, it becomes unattached and remains on the battlefield. Similarly, if a permanent that's neither an Aura, an Equipment, nor a Fortification is attached to an object or player, it becomes unattached and remains on the battlefield.

704.5r. If a permanent has both a +1/+1 counter and a -1/-1 counter on it, N +1/+1 and N -1/-1 counters are removed from it, where N is the smaller of the number of +1/+1 and -1/-1 counters on it.

704.5s. If a permanent with an ability that says it can't have more than N counters of a certain kind on it has more than N counters of that kind on it, all but N of those counters are removed from it.

704.6. If multiple state-based actions would have the same result at the same time, a single replacement effect will replace all of them.

Example: You control Lich's Mirror, which says "If you would lose the game, instead shuffle your hand, your graveyard, and all permanents you own into your library, then draw seven cards and your life total becomes 20." There's one card in your library and your life total is 1. A spell causes you to draw two cards and lose 2 life. The next time state-based actions are checked, you'd lose the game due to rule 704.5a and rule 704.5b. Instead, Lich's Mirror replaces that game loss and you keep playing.