The Magic 2012 Core Set and Duels of the Planeswalkers 2012 introduce some new terminology to the Magic universe, and the core set brings back a few things you might or might not have expected.
If you're new to Magic or looking for a refresher on the basic rules, check out the Learn to Play page.
Some keywords, like infect or exalted, show up in a set (or a group of sets, called a block) but aren't in subsequent sets by default. Other keywords, like flying and lifelink, are considered "evergreen" parts of the game. They can appear in any set, and most sets feature all of the evergreen keywords on at least a few cards.
Magic 2012 features a new evergreen keyword: hexproof!
A creature with hexproof can't be the target of spells or abilities your opponents control, but you can target it with spells and abilities normally. That means that your opponent can't use Doom Blade to destroy your Dungrove Elder, but you can still use something like Lifelink to make it better—the best of both worlds.
Like most of the evergreen keywords added to the game since its beginnings, hexproof isn't a new concept. It's the keyword version of a familiar ability seen on cards such as Troll Ascetic and Sacred Wolf. Those two cards—along with all the other cards that have text that exactly matches what hexproof does—have received updated official wordings with the new keyword.
"When [this card] is put into the graveyard from the battlefield" is a mouthful, and when people are talking about cards informally, they're more likely to say something shorter such as "When [this card] dies." Now—specifically in the case of creatures—that's what the cards say as well.
"Dies" is shorthand for "is put into a graveyard from the battlefield" that's used exclusively to refer to creatures. (Other forms of the verb "to die," such as "died," are used as appropriate.)
"Dies" and "is put into a graveyard from the battlefield" mean the same thing, so there are no functional changes resulting from this change. In other words, the new terminology doesn't change how the cards work; it just makes a certain subset of cards easier to read and talk about.
It doesn't matter how or why the creatures were put into the graveyard, so a creature dies whether it's sacrificed, destroyed, or put into the graveyard from the battlefield for any other reason. A creature doesn't die if it's exiled, returned to its owner's hand, or put anywhere else from the battlefield, nor does it die if it's put into a graveyard from somewhere other than the battlefield (such as a player's hand or library).
Cards don't use "dies" if they refer to cards that aren't on the battlefield, objects that aren't creatures by default (for example, enchantments), or groups of objects that might include some creatures and some noncreatures (for example, permanents). They also don't use "dies" if they refer to cards being put into a specific graveyard, as Nim Deathmantle does.
In addition to evergreen keywords, some recent core sets include keywords from the past. The Magic 2012 Core Set features the bloodthirst keyword from the Guildpact set:
"Bloodthirst N" means "If an opponent was dealt damage this turn, this creature enters the battlefield with N +1/+1 counters on it."
Life loss that isn't caused by damage (for example, the life loss caused by Vapor Snag) doesn't cause a creature with bloodthirst to get counters, but damage from a source with infect (such as Cystbearer) does, even though it doesn't cause loss of life.
It doesn't matter whether the damage is combat damage from an unblocked attacking creature or damage dealt by a spell or ability, nor does it matter if the player gains life later in the turn. All that matters is that at least one opponent of the creature's controller was dealt damage earlier in the same turn that the creature enters the battlefield.
Planeswalkers have been part of the game since their debut in the Lorwyn set in 2007, and by now most players are comfortable with how they work. Nothing in the planeswalker rules has changed; what follows is a refresher on the finer points of playing with planeswalkers.
Planeswalker cards are shuffled into your deck at the start of the game, just like any other cards. You can cast a planeswalker only at the time you could cast a sorcery. A planeswalker is a permanent, so when a planeswalker spell you control resolves, it enters the battlefield under your control. (Note that planeswalkers are not creatures.)
Each planeswalker has a subtype. For example, Sorin Markov says "Planeswalker — Sorin" on its type line. If two or more planeswalkers that share a subtype are on the battlefield, they're all put into their owners' graveyards.
The number in the lower right corner of a planeswalker card is its "loyalty." It enters the battlefield with that many loyalty counters on it. If it's ever on the battlefield with no loyalty counters on it, it's put into its owner's graveyard.
Each planeswalker has a number of activated abilities on it. These are its loyalty abilities. You can activate one of these abilities only at a time you could cast a sorcery, and only if none of that planeswalker's abilities have been activated yet that turn.
The cost to activate a loyalty ability is to add or remove a certain number of loyalty counters from the planeswalker. For example, the +2 symbol on Sorin means "Put two loyalty counters on this planeswalker," and the -3 symbol means "Remove three loyalty counters from this planeswalker." You can't activate an ability with a negative loyalty cost unless the planeswalker has at least that many loyalty counters on it.
Fighting a Planeswalker
Planeswalkers can be attacked. When you declare attacking creatures, you choose whether each one is attacking your opponent or a planeswalker that opponent controls. Your opponent can block as normal, regardless of what each creature is attacking. If a creature deals combat damage to a planeswalker, that many loyalty counters are removed from it.
Other sources can deal damage to planeswalkers. If a spell or ability you control would deal damage to an opponent, you may have it deal that damage to a planeswalker that opponent controls instead. So while you can't target a planeswalker with a Shock, you can have a Shock that targets your opponent deal 2 damage to one of his or her planeswalkers instead of to the player. You can't split the damage from one source between a player and a planeswalker. Damage dealt to a planeswalker results in that many loyalty counters being removed from it.