Comprehensive Rules Changes
Dozens and dozens of examples were changed to reflect Oracle text changes to cards they quoted. None changed in ways not covered by other rules changes.
These two rules talk about how to start a game with a planar deck. They said that if the top card is a plane, it's your starting plane, but if it's a phenomenon, dig deeper. But wait! They never said that plane you find when you dig deeper is your "starting plane." I cleaned up the logic so there's always a defined starting plane.
This is the rule that talks about producing mana. I was surprised to find that we never formally defined "adds mana to mana pool" as producing it, but now this rule binds together all of the various terms used for mana and mana pools.
This rule talks about unspent mana and emptying your mana pool. It's been updated to reference "unspent" mana and "losing" mana specifically. Then I took its only-child subrule and snapped it in two, then flipped the order so the more likely thing is listed first.
This rule parallels a certain other rule that just might be 106.11a (but no promises) to talk about replacement effects applying when something is "tapped for mana." We had this defined for triggers a while back, but Damping Sphere in Dominaria made us realize that the rules never actually covered replacement effects until now.
One rule (106.12) talks about one card (Drain Power) that does one weird thing (you won't believe number 100.6b). Drain Power's text changed with the "mana pool" update, so this rule also changed to match its new words. It also maintains Drain Power's existing behavior, since the card's new text certainly could be construed as a functional change without this support.
Negative numbers get converted to 0 when they're filling in a variable, unless they're doubling or setting a player's life total or setting a creature's power or toughness. Now we can also double a creature's power or toughness! The rule's been updated to collapse the logic a little bit to cover all of the situations without repeating so many phrases.
Here's where we define chapter symbols. This rule makes it clear that they represent keyword abilities, just like the level symbols on those leveler cards from Rise of the Eldrazi a couple years back (certainly not eight years, no way was it that long ago).
Once upon a time, Delraich (and several other cards with longer names that I don't want to type over and over in this example) read "You may [cost] rather than pay Delraich's mana cost." If you wanted to use Back from the Brink to make a Delraich, it sure sounded like you could pay its other cost, since the ability's talking about Delraich's cost. This rule used to say that sure, you could do that.
But lo! One of the non-functional templating changes was to change this to "You may pay [cost] rather than pay this spell's mana cost." This templating change didn't force this interaction to change, but it did make us re-examine it. We decided that it no longer looks like a natural or intuitive interaction with the new text, so the rule's been changed. Delraich's alternative cost only applies while it's on the stack as a spell.
I just chopped some text that no longer appears on cards so the examples are only things that exist. Nothing to see here.
This new rule defines "target" when used as a noun ("any target") rather than as a demonstrative adjective ("target creature"). If you entirely understood that sentence the first time you read it, you're cool.
These rules clear up some ambiguity surrounding the "if you do" on such search effects as "You may search your library for a Jellyfish card, reveal it, put it onto the battlefield, step on it, scream, and regret your life choices. If you do, shuffle your library." It's legal to choose to search your library even if you know you won't be able to find a card or perform the later actions (perhaps you're in a library (the building, not the stack (a pile, not a game zone) of cards) where screaming isn't allowed), and "if you do" checks only whether you searched (perhaps you made better choices and didn't find a Jellyfish at all).
Here's where we say that Saga is an enchantment subtype. That's surely all the support it needs, right?
22 years after the Alliances story ended and Jaya Ballard became a Planeswalker, Jaya is added to the list of planeswalker types. Welcome aboard, old friend. Please try not to set fire to my rulebook.
Here's the legendary sorcery rule. Other supertypes get bumped down for being less super. Note that this rule is not the "legend rule." That rule is 205.4d.
Some enchantments are Sagas! Great! I'm sure we'll talk more about what that means later.
Here's where we talked about the planeswalker damage redirection rule. Now we talk about how that isn't a thing anymore.
Ooooh, here's a rule talking about the turn-based action that puts lore counters on Sagas. Surely it's time to explain all about how they work! Wait, no, it's not. Let's move on.
Two-Headed Giant games have an "attacking team" and a "defending team." But wait, you say—don't Archenemy games have those, too? Did you actually say that? Because I bet you didn't, but I'm going to pretend you did anyway. Excellent question, reader! This rule has been updated to apply those terms to all games using shared team turns.
Fight with Fire does something no card has done before: If you pay its additional cost, it throws out the whole targeting requirement and creates a new one. The rules already handled adding targets only if an additional cost was paid (like Goblin Barrage in this set), and now they handle replacing the target selection entirely.
These rules about casting things in certain situations are pretty obvious in context, but they don't actually say that you can begin to cast those things "as though they had flash." Now they do!
One of the Dominaria changes was saying that spells can't be countered, dropping "by spells and abilities." This means that spells that fizzle* shouldn't actually be countered anymore—they just go to their owner's graveyard and don't resolve, but they don't use the keyword action of "counter" to do so. This is a nonfunctional change with the exception of one weirdo: Multani's Presence.
*Yes, fizzle. I'm a linguistic descriptivist, and people want a shorter way to express this, so I whole-heartedly endorse saying "fizzle" in non-technical contexts (for example, not in the Release Notes, where I use many more words to express this). We very briefly considered resurrecting it as an official term and rejected it.
This rule defines "historic." What is historic? It's a word. A word that we gave a special meaning to, like "die." The next time we have a word just redefined like this for Magic, I'll probably create a whole new section to talk about them, but this update's big enough as it is.
Hey, it's a new keyword action: double! (I can hear Rosewater smile from over here as I type this.) Because it's up for grabs in any set, it gets to go alphabetically in the early set, and bumps down all the other keyword actions. And then, because we've defined one use case for using the word "double" in Magic templating, we had to define all the existing uses.
The rules for exchanging zones could be read to mean that it's impossible for Morality Shift to do anything if your graveyard or library is empty. That's not what we want, so the rule's been updated to make sure that's possible.
When a creature fights itself, it deals one big, walloping punch to itself. Note that I said "one"—like any other fight, the damage is all dealt at once. This rule's been cleaned up so it doesn't sound like it's two separate damage-dealing events.
The equip rules gained two new child rules to discuss the "equip [quality]" variant appearing on Blackblade Reforged.
The hexproof rules gained two new child rules to discuss the "hexproof from [quality]" variant appearing on Knight of Grace and Knight of Malice. Aren't variants cool?
I'm touching another phasing rule, which is probably a sure sign of either genius or madness. This addition makes sure that the leaves-the-game procedure for multiplayer rules can find phased-out objects, and it makes sure that objects never get locked in phased-out limbo forever when players leave the game.
We noticed that storm and gravestorm used antiquated language to talk about copying spells. Not like "when thou castest this spell," but "put a copy of it onto the stack." They've been updated to use more modern terminology for copying a spell.
This is the rule for the state-based action that cleans up Sagas, which we'll surely discuss soon. Other state-based actions are bumped down. This rule comes with two fun facts:
One, this is the only state-based action that uses a sacrifice to change the zone rather than simply putting the object into its owner's graveyard. Saga reminder text was tough to write, and this unusual behavior is a concession to improve the words.
Two, the state-based actions are listed down to x now! What will happen when we hit z and then need another? I'm as excited to find out as you are!
Aw yiss, it's finally time for rules all about Sagas! Okay, now that's done, moving on.
Here's the big Two-Headed Giant change—we're no longer dealing with "attack the team, use some mental gymnastics to figure out the defending player." Now you simply attack players or planeswalkers, not the team.
This results in a handful of changes: Propaganda effects are worse, but prevention effects can be used sensibly. Plainswalkers and planeswalkers both behave pretty much the same, except you can't attack one player and call the other your defending player. Saboteur triggers ("when this deals combat damage . . . can be anticipated more meaningfully.
These changes bring Two-Headed Giant's combat exactly in line with Archenemy, using the same shared team turns system of combat. The only difference is that the team's life total goes down rather than the individual's.