Hello, and thanks to all who provided feedback on suggestions for rules articles. The topics that seemed to generate the most interest were last known information, and the priority/stack timing system. Because the latter topic is so deeply intwined with turn structure, I'll be talking about it as well. Yes, this means I won't be getting into the intricacies of 418.5 and layers, characteristic setting abilities, dependency, and timestamps. If there's enough interest, you never know, I might write an article on that some day.
Last Known Information (LKI)
LKI is one of the most misunderstood topics in the rulebook. It can be difficult to determine exactly when and when it doesn't apply. Basically the gist is this - the game is looking for information about something, but that something has moved, so we just look at what it was when last in play. Here are some key facts:
LKI only applies when a spell, activated ability (which contains a colon : ), or triggered ability (which begins with "at", "when", "whenever") is resolving. It cannot apply to static abilities or determining whether or not a triggered ability will trigger.
LKI only applies if the game is asking about information about something.
LKI only applies when whatever we're looking for information on has changed zones since the spell or ability was played, triggered, or put on the stack.
Let's look at a simple example:
Let's say Tangle Wire has two counters on it, and is destroyed in response to its second ability. What happens here is LKI applies. This is a triggered ability that is resolving. We are looking for information about the Tangle Wire, and it's changed zones (moved from in play to the graveyard). Therefore, the player will have to tap two permanents.
A slightly more complicated one:
Player A activates his Prodigal Sorcerer to deal a damage to one of Player B's creatures. In response, Player B gives his creature Protection from Blue. In response to that, Player A sacrifices his Prodigal Sorcerer to some other ability. What happens here? The answer the game wants to know the color of the source of the ability, the Prodigal Sorcerer, to see if it's blue. The Prodigal Sorcerer has also changes zones. So we look at its last occurance in play, and at that time it was blue, so the ability will be countered on resolution because the target is illegal due to the protection.
Finally, here's an example from Pro Tour Atlanta that sparked some discussion among the judging staff:
Genju of the Cedars is enchanting a Forest. Its controller activates its ability, to try to animate the Forest. In response, the opponent destroys the Genju. What happens? Let's look at the exact wording of the ability's effect: "Enchanted Forest becomes a 4/4 green Spirit creature until end of turn. It's still a land."
Offhand, it might appear that since the Forest is no longer enchanted, that the effect will do nothing once it resolves. This is incorrect, however. The ability (something resolving? check!) must determine what the Genju is enchanting (information about an object is needed? check!), but the Genju is no longer in play (the object we need information about changed zones? check!) so we refer to the permanent the Genju was enchanting when it was in play,
Important Note! Remember that Last Known Information uses the information it had when most recently in that zone, which may not be the same as the information it had when the spell or ability was played or triggered. Imagine an ability that said "Whenever a creature goes to the graveyard from play, ~this~ deals damage to target creature or player equal to that creature's power." This uses LKI to determine the power. Suppose the creature was a 5/5 and Mutilate was played for X=5. How much damage would it deal? The correct answer is none, because the power was 0 before the creature left play, so its last known power was 0.
Priority, State Based Effects, Triggered Abilities, and the Stack
The following is the flow chart of how this stuff works. Special thanks to Yawgatog for making the flow chart to my specifications. A diamond is a question that branches off depending on the answer, while a rectangular box is an action to take. On the diamonds, follow the green path if the answer is yes and the other path (usually red) if the answer is no. Many phases or steps of the game start off with a special action. In the draw step, you draw a card. In the declare attackers step, you declare attackers. In the declare blockers step.... well... you get the idea. Anyway, after that, the game proceeds using this flow chart until it's done (meaning the current step and/or phase ends).
State Based Effects are a series of things that, if true, cause something to happen in the game. For beginners, I will try to describe them as the things they might think of as happening automatically (a creature dying with lethal damage, etc.). For advanced players and judges, I try to describe them as corrections to game states the game views as "illegal". There's a list of them in rule 420.5 if you want to know what they all are. And, when judging an event with Sheldon, be sure to know which SBE you would be if you were one (yes, he asked me this... and don't say "poison counters", be original!).
Triggered abilities work a bit differently. Most players are somewhat confused on the difference between the ability *triggering*, and the ability *being placed on the stack*. The ability triggers just after the event happens. Right after my Eternal Witness comes into play, it's ability triggers. Abilities can trigger at any time, and don't follow the timing scheme above. On the other hand, placing the triggered ability on the stack is done as indicated below. It just "collects" what has triggered so far and places them on the stack.
Of note here is that they are placed on the stack in APNAP (all the Active Player's first, and then all the Non-Active Player's after that, with the understanding that if a player has more than one, he or she chooses the order among them they go on the stack in). It doesn't matter the order the abilities triggered in, and in many cases they will have triggered at the same time (e.g. multiple creatures with "leaves play" triggered abilities dying to Wrath of God). Also, when you place the triggered ability on the stack is when you choose targets for the ability if it has any (not when it triggers). This makes it possible, for example, to Tooth and Nail Eternal Witness (and another creature) into play, and get the Tooth and Nail back into your hand with Eternal Witness' ability.
I'll try to go through an example of the flow chart here (just one, it's long and a little boring). We'll begin with the First Main Phase of Player A's turn. Player A has several Mountains and Iron Star in play, while Player B controls Solemn Simulacrum enchanted with Control Magic he used to steal if from Player A, and several Islands. Both players are at 20 life.
No SBEs apply, so we move on
No abilities have triggered, so we move forward again.
The active player, Player A, receives priority, and plays Earthquake. This triggers his Iron Star.
We do another SBE check, nothing applies
The Iron Star triggered ability, having triggered, is placed on the stack.
Player A receives priority again, and this time passes it.
Another SBE check, this time on the non-active player part of the flow chart. Still nothing, though.
No triggers again.
Player B receives priority this time, but doesn't have any responses, so also passes priority. Note that both players have passed in a row now without playing anything.
Since the stack is not empty, the top object on the stack - the ability of Iron Star - resolves. Player A chooses to gain 1 life.
And we're back to the SBE check again.
Did you guess we're looking for triggered abilities here and didn't find any? If so, congrats. You're right.
Player A receives priority, and has nothing to do, so opts to pass priority.
Another SBE check (nothing applies)
Another triggered ability time, but nothing's triggered still
Player B receives priority again, and, again, chooses to pass. This is now in succession also.
The stack is not empty, Earthquake is on it, and it resolves. Two damage is dealt to Player A, Player B, and Solemn Simulacrum.
SBE check! Wait, this time one applies! Solemn Simulacrum has damage equal to its toughness and is destroyed going to Player A's graveyard (since he owned it after all). This triggers its leaves play triggered ability, and since B controlled it at the time, it's Player B's triggered ability..
We do another SBE check, since that time one applied. Now another one has applied. There is a Control Magic in play without enchanting a creature. It goes to Player B's graveyard.
We do yet a third SBE check, but nothing applies now, so we move on.
An ability has triggered since the last time we checked for these, so now the Solemn Simalacrum's triggered ability is placed on the stack
Player A receives priority and passes.
Another SBE check (nothing).
Another triggered ability check (move along, nothing to see here).
Player B receives priority and passes. Both players have passed yet again.
The top object on the stack - the Simulacrum's ability, resolves. Player B draws a card.
SBE check again (aren't you sick of SBE's by now? still nothing)
Triggered ability check again (do I need to say nothing again?)
Player A gets priority and.... passes!
SBE check again (probably not)
Triggered ability check again (is anyone even still reading this?)
Player B gets priority and, finally, passes.
Since the stack is empty, the main phase ends!
The game would then continue on with the combat phase.
Hopefully, this brief example coupled with the flow chart gives you an understanding of exactly how the game proceeds through the priority system. If you have any questions on anything I've talked about in this article, I will be monitoring and replying to the forums. I can also answer questions via e-mail, or for even faster responses, look for LeeSharpe or Lee_Work on Efnet's #mtgjudge
As this is my last article before turning the authorship back over to Sheldon - who I'm sure has some great articles in store -- I'd like to thank the following people:
* Shawn Doherty, for certifying me for L1 and L2 and giving me many opportunities
* Rune Horvik, for a lot of assistance and help, as well as the priveledge of editing for him
* John Carter, for many things (he probably knows them all)
* Scott Lelivelt and Lee McLain, for helping me improve my player management skills
* Sheldon Menery, John Shannon and Matt Villimano for conducting my informative (and successful!) L3 interview (and Sheldon again for letting me write these columns).
* Andy Heckt, for his many improvements to the DCI Judge Program
* Cathy Nicoloff, for creation and maintenance of Sibyl, which saves me (and others) so much time :)
* The #mtgjudge community, for some great discussion and socialization
* Every judge out there who allows players to play in tournaments. You keep the game alive.
Thanks for reading!
--
Lee Sharpe, lee DOT sharpe AT gmail DOT com
DCI Level 3 Judge
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