Comprehensive Rulebook Changes
What are the Comprehensive Rules?
Magic is complicated. No, really. When you have over 11,000 interchangeable game pieces, you get some freaky interactions. The Comprehensive Rules cover everything the game has ever come up with, from basic game play structure, to every keyword ever, to entire pages dedicated to single bizarre cards (hello, Karn Liberated!) The Comprehensive Rules are, well, comprehensive ... but they're also obtuse, unfriendly, and looooong. They're not intended to be a player resource—they're a judge resource, a rules guru resource, and a place to store definitive answers. In fact, I honestly recommend never reading them. For a much friendlier rulebook that is intended to be a player resource, check out the Rules Page and download the Basic Rulebook (2MB PDF). It doesn't have sections about phasing or subgames ... but you'll never miss them.
This change came about when we were looking at the Magic 2012 "learn-to-play" insert that gets included in many of our products. It felt weird that the name of the variant, Planar Magic, didn't appear on the Planechase packaging at all. With Archenemy and Commander, the name of the format matched the name of the product, so we decided to do the same with Planechase. This change appears in many rules and cross-references.
Speaking of Planechase, Tember City's planar type never made it into the official list. Welcome to the Multiverse, Kinshala!
510.1c, 510.1d, 510.1e
These changes impact the way you assign combat damage when a creature blocks or is blocked by multiple creatures. Previously, you had to assign the combat damage of each creature fully before another creature's damage could be assigned. However, the rules also implied that you couldn't assign combat damage to a creature unless each creature before it in the damage assignment order was assigned lethal damage. But you could consider the combat damage assigned by other creatures in the same combat damage step. It was a strange paradox. It was further complicated by rule 510.1c's fourth example, which didn't follow that rule at all!
Now, the legality of any combat damage assignment is only checked after all combat damage is assigned. If anything is illegal, you back up and do it again. Perhaps an unrealistic, complicated example would be helpful.
Say you were attacking with a Necroskitter with a +1/+1 counter on it (so it's 2/4), a Runeclaw Bear (2/2), and a Canyon Minotaur (3/3). Your opponent controls two 5/5 creatures that can block any number of creatures. Each one of them blocks each attacking creature. Furthermore, you set the damage assignment order for each of your attackers the same way: first the cleverly named Blocker A, then Blocker B.
When you assign combat damage, you pick the Necroskitter to go first. You obviously want to get a -1/-1 counter onto each of the blockers, so you assign 1 damage to each of them. Previously, it wasn't clear that this was legal. Hopefully it now is! You then go on to assign all 3 damage from the Canyon Minotaur to Blocker A, and 1 damage to each blocker from the Runeclaw Bear. In total, A (first in line) has lethal damage assigned to it and B has 2 damage assigned to it. This is all legal, so you're good to go.
Put in layman's terms, assigning combat damage is "do what you want; we'll check it at the end."
Information saying "dies" would be coming with the Magic 2012 Core Set is now unnecessary. This language was also taken out of the "dies" glossary entry.
This rule dealt with cleaning up after a player leaves a multiplayer game. In order, all objects owned by that player leave the game, spells and abilities controlled by that player cease to exist, and effects which give the player control of any objects or players end. That middle part was intended to clean up objects not represented by cards: copies of spells, activated and triggered abilities, and the like. However, with Commandeer, it was possible for a player to control a spell on the stack represented by a card that didn't leave the game. The rules then want to make that card cease to exist. Making cards you don't own cease to exist is not generally considered sporting behavior, especially if you try to use fire or a hacksaw or something. Switching the order of the last two parts of this rule cleans it up.