Comprehensive Rules changes
107.4h
This rule defines {S}, the snow mana symbol, which on cards looks like a snowflake. Prior to Kaldheim, this symbol was used exclusively to denote a cost, payable by one mana from a snow permanent. Now in the time of Kaldheim, things have changed a bit. First, we now have snow spells that add mana, so "snow permanent" becomes "snow source." Second, on cards like Search for Glory, we use {S} to reference the amount of mana spent from a snow source.
111.10d
A while back, we released a special Secret Lair drop featuring characters from The Walking Dead. This included a new predefined token, a Walker. That release didn't have a rules update, so we told the Walker to walk to the next update so it could be included in the rules. Well, that took a while. But it finally got here, so Walker tokens (2/2 black Zombie creature tokens) are now defined.
111.10e
The new planeswalker Niko Aris is traipsing around Kaldheim, and their specialty is Shards, a new predefined token. A Shard is an enchantment token with "{2}, Sacrifice this enchantment: Scry 1, then draw a card," giving friends of Niko superior card-sifting and card-drawing potential.
113.11
This rule was written to support the cycle of Archetypes from Born of the Gods. Each of them had an ability that said creatures your opponents control lost and couldn't have or gain a particular keyword. Unfortunately, they didn't mention keyword counters, so that oversight was corrected. Giving a flying counter to a creature under the effect of Archetype of Imagination won't actually give the creature flying.
116.2h
THERE
119.4
This rule in the life section included the fact that players can always pay 0 life, but had it in parentheses, which seemed to minimize its importance. Is it even a real rule? Why is it in parentheses? What is it hiding? Anyway, we bumped it out of the loving embrace of the parentheses and into a real subrule, including a clarification that you can pay 0 life even if an effect says you can't pay life.
120.4
This rule includes information on how to process damage. The first part is a check to see if an effect redirecting excess damage applies. We restructured the rule to (we hope) cleanly lay out how to know what excess damage is. There are three relevant cases: versus a creature, versus a planeswalker, and versus a permanent that's both. Sup, Gids?
120.10
This new rule in the damage section is for Toralf, God of Fury and Aegar, the Freezing Flame. These two cards have triggered abilities that look back and see if excess damage was dealt. To be thorough, the same methods used to determine excess damage outlined in 120.4 are reiterated here. This time, though, we're looking at what did happen to determine if abilities should trigger, as opposed to looking at what would happen to determine if replacement effects should apply.
122.8
This is the rule that handles cards like The Ozolith, explaining what happens when told to put the counters on a permanent that has left the battlefield onto another permanent. Technically, the counters on the first object no longer exist, so they can't be moved. Rather, new counters are put onto the second permanent, matching the number of each kind of counter that was on the first permanent. The functionality didn't change; we just tweaked some of the language to (we hope) be more clear.
201.2
These rules discuss how to determine if two or more objects have the same name, if two or more objects have different names, or if one object has a different name than another object or group of objects. You might think this would be straightforward, and it often is, but objects in Magic can have no name. And sometimes they have multiple names. And at least five of you out there play with Spy Kit, and you have creatures with lots of names!
We cleaned up a lot of the language here. One quirk to remember is that an object with no name can't have the same name as any other object, even another one with no name. Two objects have the same name if they have at least one name in common.
201.4a
We beefed up this rule to account for Cosima, God of the Voyage to make sure that when you exile Cosima, the ability it gains points at the right object, namely the Cosima in exile, not the object it was on the battlefield.
205.3h
Rune and Shard take their rightful places in the list of enchantment subtypes.
205.3j
There are two new planeswalkers joining the roster with this set: Niko and Tyvar. Long may they frustrate your opponents.
205.3m
Phyrexian is now officially a creature type, but it's important that you don't tell anyone.
406.3b
Sometimes you're given permission to cast a spell with certain qualities from among face-down cards in exile. If you're allowed to look at the cards, as you are most of the time, you can look at them to determine if they qualify. But sometimes a card is exiled face down and you don't have permission to look at it. In this case, you can't start to cast the spell (thereby revealing it and putting it on the stack face up) to see if it meets the qualification. Put another way, you can't use the cast permission as an excuse to look at a card you wouldn't be allowed to otherwise. This new subrule, along with the new subrule 601.3f, clarifies that case.
601.2a
Nestled amongst other rules that describe the casting of a spell, this rule tells you to first put it on the stack. It stays there until it resolves, it's countered, or a rule or effect moves it elsewhere. "Rule" was missing from that list, and now that a spell that tries to resolve with an illegal or missing target isn't technically countered, it felt right to include it.
607.1d and 607.2p
Up until Kaldheim, linked abilities always appeared on a single object. Usually, one ability has you make a choice or exile some cards, and the other ability refers to that choice or the exiled cards. Tibalt, Cosmic Impostor, true to his nature, messes with the system a bit, creating an emblem with an ability that is linked to Tibalt's other three abilities. These new rules allow for such a thing.
608.3
This rule details what happens with a resolving permanent spell. We tweaked some words around copies of permanent spells and how they resolve and become tokens.
701.12b
Say two creatures are scheduled to fight. But then one of them chickens out and leaves the battlefield or otherwise becomes an illegal target of the spell or ability that is going to have them fight. Previously, it wasn't completely clear that the other creature didn't fight. We knew it didn't deal damage, and it definitely wasn't dealt damage. But it was still a legal target of the spell or ability, so did it fight? The answer is no. Sorry, Foe-Razer Regent fans. And sorry to everyone who bought the pay-per-view.
702.33a and 702.132a
These are rules for flashback and jump-start, two abilities that allow you to cast spells from your graveyard. Notably, they are the two abilities that can be granted to instant and sorcery cards in your graveyard. So far, so good. But what if the instant card in your graveyard that picked up flashback or jump-start is actually the front face of a modal double-face card with a permanent face on the back? We added a few words to clarify you can cast only instant or sorcery spells using flashback and jump-start.
702.141
This is the greatest rule addition of all time. I wrote this in an unprecedentedly awesome way. (Yeah, it's the rules for boast.)
702.142
Curious reader, seeking rules knowledge. I knew you'd come. (Yeah, it's the rules for foretell.)
704.6d
For the Commander players out there, this is the rule that describes how you can send your commander to the command zone from your graveyard or exile if that card was put there since the last time state-based actions were performed. You may remember this as the rule put in a while ago that lets "dies" triggers on commanders function. We changed "that card" to "that object," and here's why: Say your commander was exiled by something like Otherworldly Journey. You don't want to send it to the command zone, as you're expecting it to return to the battlefield all by itself, and with a shiny new +1/+1 counter to boot! But before that happens, your dastardly opponent casts Containment Priest. That cad! Under the old rule, it would be too late to rescue your stranded commander, as the card that represents it has been in exile for some time. But if it can't re-enter the battlefield, it becomes a new object that was just exiled (400.8). So now with the new rule, you have another opportunity to send your commander to the loving embrace of the command zone. (We made the same tweak to 903.9a in the Commander section.)
706.9
This rule is all about modifications or exceptions to the copying process. We reordered some subrules to make them flow more logically without changing their underlying meaning. One notable tweak for cards like Glasspool Mimic: If the exception states that the copy becomes a certain creature type or types "in addition to its other types," the copy will successfully pick up characteristic-defining abilities that define creature type, like changeling or the one Tajuru Paragon has. All of this leads to the (we hope) intuitive result that a Glasspool Mimic copying a creature with changeling ends up with all creature types.
706.9f
This new subrule in the copy exception section addresses a new kind of exception seen on Moritte of the Frost. Moritte may or may not pick up changeling and enter with two +1/+1 counters on it depending on if it's a creature. This rule makes that exception work smoothly, telling you to look at what Moritte would be ignoring in that exception to then determine if the exception applies. Simply put (ha ha), if Moritte would end up as a creature, it'll have changeling and the counters. If not, it won't.
721.2b
Did you know that you can now create a copy of a creature spell cast using mutate? Fun, right? We tweaked the merging with permanents rules to make mention of this wacky fact.
New Glossary Entries
Boast, foretell, foretold, Gold token (oops), Shard token, Walker token
Revised Glossary Entries
Snow mana symbol
Introduction
Comprehensive Rules Changes
Oracle Changes